If a ship's lamp carries a brass plate engraved with a type name, a number, a country and a year, it is almost certainly a replica. Something like:

Anchor Light No. 1235 Great Britain 1919

That reads convincingly. It corresponds to no approval system of any country, and it reads like a caption written for somebody looking at an object on a shelf.

Genuine ship's lamps do carry years. A rule that treats any date as a warning sign will throw out good lamps. The question is what the date belongs to.

A year beside a maker's name is normal. Makers put their own name on their work, and sometimes a year with it: a year of manufacture, a date of establishment, a patent date. American lanterns in particular carry patent dates, and a patent date is useful evidence, because the lamp cannot be older than it.

A year inside an approval number is normal. There it is part of the number rather than a statement on its own. In a German number the last two digits are the year of approval. Dutch certification numbers issued from 1965 are six characters, of which the first two give the year.

A year attached to the type of lamp, with a country, is the replica pattern. Anchor Light No. 1235 Great Britain 1919 names no maker and resolves into no approval system. It describes the object to its owner.

Every country that inspected ship's lamps had its own system, and none of them looked like that plate. The systems are set out under Identifying a Ship's Lamp: a letter and digits in the Netherlands, a number in several parts in Germany, an anchor in a circle in Belgium, the words Marine marchande in France, a visibility range in nautical miles in the United States.

Britain is the row the replicas most often invoke. British surveyors were inspecting lanterns from 1849, one of the oldest regimes anywhere, but the system worked by approving makers' patterns rather than by numbering individual lamps. No British national marking that gives a lamp a number and a year has been traced.

So "Great Britain 1919" is not a copy of a British approval mark, because there was no such mark to copy. That does not rest on the stronger claim that no maker ever put a country and a year on a plate. Makers lettered their products as they liked, and across a century and a half and dozens of countries someone probably did. The point is narrower: a plate of this kind matches no approval system, so it carries no evidence.

Japan is the exception worth knowing. A Japanese lantern does carry a riveted plate with a type approval number, the type of light and a date. It names a Japanese ministry and a Japanese maker, in Japanese. It does not say "Great Britain" in English.

The plate settles the obvious cases, and most lamps do not carry one. Then the judgement rests on the object, and four things are worth going through. The condition, because a lamp that went to sea shows it. The name the lamp gives itself, because the types of navigation light are a finite list. What a search turns up, because a replica is a production run. And whether the parts a working light needed are there at all.

A lamp in effectively new condition is reason to doubt.

New old stock exists: a lamp that is genuine but was never put into service. On German lamps there is even a way to recognise it, since glass that never went to sea has no scratched test mark. But a pristine lamp needs other evidence before it is treated as new old stock.

A lamp that hung on the outside of a ship shows the marks of time. Salt, spray, sun and handling leave traces on copper and brass. A lamp that hung inside shows lighter traces, but usually some.

Where to look: the underside and the feet, where water stood; the hinge and the closure, which were worked every day; the inside of the chimney and the burner gallery, which should be sooted; and the seating the glass sits in.

The types of navigation light were defined by regulation and the list is finite: sidelights, masthead light, sternlight, towing light, anchor light, all-round light, not-under-command, bicolour and tricolour, the fishing lights, the signal lantern. The whole set is on Types of Navigation Light.

A name that sounds maritime but appears in no regulation is a warning. "Clipper Ship Lamp" is not a category of navigation light. Neither is "Cargo Light". A genuine lamp from a ship is a sidelight, a masthead light or an anchor light, because it is defined by the arc it shows. A name that describes the kind of ship, or its cargo, rather than the job of the light, is a decorator's name.

Spelling is worth a glance too. A binnacle lamp is a real object, the light for a compass binnacle. A plate reading "Binacle Lamp" has one n too few.

If there are marks or names on the lamp, put them into a search engine. A genuine lamp of a given approval number and year exists in small numbers, while a replica is a production run, so the same lamp turning up again and again in equally good condition is a signal.

If there is nothing written on the lamp, Google Lens can help, since it searches from a photograph and will often bring up comparable lamps and listings.

Two refinements. Search the approval number whole and also in parts, because a German number can be checked against the real approval holders and the years the register covers. And search the maker's name separately from the lamp, because real makers have histories, addresses and date ranges, several of which are documented.

The tests above are mostly negative. These are the features a working navigation light needed in order to be lawful, which a decorative lamp has no reason to reproduce properly.

A screen on a sidelight. A long inboard plate running fore and aft, prescribed at 0.90 m ahead of the light by the French decree of 1858 and at least three feet by the rules of 1948. It is awkward, it takes up room, and it is the part that made the lamp legal, so a replica often omits it or fits a token version.

Thick, worked glass. A genuine lens is heavy, usually a Fresnel or prismatic lens moulded with stepped rings or cut prisms. Some carry a glassworks mark, such as the GGG triangle of Genthe Glas. Thin, plain, light glass in a lamp claiming to date from the regulated era is wrong. See Glass, Lenses and Burners.

A burner and its gallery. The burner is often missing, but the gallery it sat in should be the right size and shape for a real one.

The right metal. A British-registered masthead or anchor lantern had to be of galvanised steel or entirely of copper.

Marks that agree. The number in the glass and the number on the housing should match. Where they differ the lens is not original, which does not make the lamp a replica but does make it an assembly.

Weight and fit. Genuine lanterns were built to survive. Hinges close properly, the glass seats in its ring, and the whole thing is heavier than it looks.

A lantern was offered carrying the text "Holland Amerika Lijn — SS Nieuw Amsterdam — 1st Class Only". The seller said it had been given to the first first-class passengers of the SS Nieuw Amsterdam after her launch. The same story appeared with a listing on Catawiki, which was presumably where the seller had it from.

Holland America Line were contacted directly and referred the enquiry to the association De Lijn. The association answered that the lantern does not come from Holland America Line, and that the company never gave away or sold a brass gift or souvenir of any kind. They added that somebody is placing this same plate on a wide variety of different products.

Three things follow. A story is not provenance, and the more precise and appealing it is the more worth checking. A claim that circulates among sales listings gains nothing by being repeated. And the organisation named is often willing to answer: shipping lines, shipyards, glassworks and painting firms frequently keep archives, or have an association that does.

In each case the giveaway is a legend that reads like a museum label, with a year no marking system ever presented that way.

Before the four, one thing they share. Look at the plates on the Anchor Light and on the Clipper Ship Lamp. Same rectangular brass plate, same twisted-rope border, same four domed copper rivets, same lettering. By their own inscriptions these two lamps come from different countries and are fifty years apart. Their plates were made in the same workshop.

Clipper Ship Lamp, "No. 1255 Dumbarton, Scotland 1869"

Three problems. "Clipper Ship Lamp" is not a type of navigation light and no regulation defined one; a lamp from an 1869 vessel would be a sidelight, a masthead light or an anchor light, because in 1869 the governing rules were the Order in Council of 9 January 1863, which defines lights by their arc. Britain assigned no national lamp numbers with years. And the place and the year belong to a famous ship: the Cutty Sark was built at Dumbarton in 1869, the contract signed with Scott & Linton on 1 February, completed by Denny Brothers after Scott & Linton went into liquidation, and launched on 22 November.

Cargo Light No. 3954, "Great Britain 1939"

"Cargo Light" is not a category of navigation light either. It describes what the ship carried, which is the one thing a navigation light does not say. Note also that the plate runs Great Britain together as one word.

"Binacle Lamp 1917"

A binnacle lamp is genuine: the light for a compass binnacle, one of the lanterns a ship carried to light her own instruments rather than to be seen from outside. This plate is spelled "Binacle" and carries a bare year in the same pattern as the others.

Anchor Light No. 1235, "Great Britain 1919"

The most plausible of the four, because an anchor light is a real and common type. A genuine British anchor lantern of around 1919 would be of galvanised steel or entirely of copper, would carry a maker's name rather than a national number, and would show the wear of a lamp hoisted on a line in all weathers.

The four above are decorative objects pretending to be antiques. This one is different. The model is real, and one of its two marks is not.

In the latter part of the 1980s, reproductions of early Perkins marine lanterns were made overseas and put on the United States market. They are hard to spot because they look antique. Hobson gives the tell as the words "Perko" and "Brooklyn NY" appearing together on an oval brass tag.

That is too broad a rule. Perko and Brooklyn belong together on a genuine lamp. The firm's own catalogue of 1936 is headed Perkins Marine Lamp And Hardware Corp. of Brooklyn and states that the PERKO trade mark is by then widely known. The two names ran side by side for a quarter of a century, until the Brooklyn works closed.

The lantern below carries both marks at once, and the difference between them is the lesson.

The riveted plate is struck deep, carries a beaded border, abbreviates the company to HDWE. CORP. and reads REG. TRADE MARK. The stamp pressed into the base is shallow, has a plain border, spells HARDWARE out, and reads REG. TARDE MARK. A company does not misspell its own registered trade mark. Whatever else is true of this lamp, that second mark was not made in Brooklyn.

The model itself is in the catalogue. It is the 10 Day Anchor Light, figure 596 of 1936: fourteen inches high on a seven-inch fount, guaranteed to burn at least ten days on one filling of good kerosene. The same catalogue names its standard burner, the Long Time Burner, and its chimney, a short Perko-marked barrel an inch and a half across. The burner on this lamp is marked WEDGE, a name that appears nowhere in that catalogue.

So the lesson generalises, and it is narrower than the rule it replaces. A mark can be checked against the company's own catalogues, and a copy good enough to fool the eye is often still wrong about a single letter. The chronology of Perkins and Perko markings is under Identifying a Ship's Lamp.

The absence of a mark. A British commercial lantern may never have carried one. A German mark scratched in the glass is faint and easily overlooked, and a replacement lens carries no mark at all. A naval lantern has a pattern number and no approval. Plenty of genuine lamps have nothing on them.

An electrical conversion. A genuine lantern may have been wired at some point, in service or afterwards. A conversion is not a forgery, though the burner has usually gone with it.

A repaint. For small sailing craft the paint was required by the regulations of 1858 and 1863, and on zinc lamps it was protection. See Painted Ship's Lamps. Paint over a mark is one reason a genuine lamp appears to have none.

The purpose of all this is not to catch out sellers, most of whom are passing on what they were told. It is to know what you are buying, so that a decorative lamp is bought as a decorative lamp and at a decorative lamp's price.

Primary: Enquiries to Holland America Line and to the association De Lijn; Order in Council, Osborne House, 9 January 1863; decree on the lighting of ships, France, 28 May 1858; Regulations for Preventing Collisions at Sea, 10 June 1948; Bundesamt für Seeschifffahrt und Hydrographie, BSH-Zulassungen bis 31.12.1998 — See; Perkins Marine Lamp And Hardware Corp., catalogue no. 75, 1936; replica lamps and marks in the author's collection.

Secondary: A. Hobson, Lanterns That Lit Our World, Book 2, section II, for the Perkins and Perko history and the 1980s reproductions; R. Bahr, MPhil thesis, University of St Andrews, 1998; German collectors' reports on the Pelam forum, 2020 and 2022; West Dunbartonshire Council museums and galleries collections, on the building of the Cutty Sark.