# The Weight Is Written on the Object > Two Roman silver vessels in the British Museum carry their own weights punched into the base. One agrees with the scales to within 68 grammes and the other is out by 900. For metal, weight is the identifier that was recorded first and is checked least. > The Study - 2026-09-07 > Canonical HTML: https://iconotheca.com/study/the-weight-is-written-on-the-object/ ## Key points - The Corbridge Lanx carries its ancient weight punched into the base in dots: fourteen Roman pounds, three ounces and two scruples. The British Museum converts that to 4,668.5 grammes and weighs the dish at 4,600, so the object and its own label agree to within one and a half per cent after sixteen centuries. - The Projecta Casket carries the same kind of inscription and does not agree at all. Twenty-two Roman pounds and three and a half ounces converts to about 7,299 grammes on the museum's own constants, and the casket weighs 8,200. The gap is roughly 900 grammes, it is not explained on the object's record, and it survives any plausible value for the Roman pound. - Weight is the one physical measurement that was recorded because the metal was money, so it exists for silver and gold at dates when nobody was writing down dimensions. - A falling weight is a record of use. Paul Revere's Sons of Liberty bowl was announced in 1768 as weighing forty-five ounces and now weighs 43 ounces 16 and a half pennyweight, a loss of about 36 grammes to finishing and to two and a half centuries of polishing. - A rising weight caught a theft. The hippocamp brooch on display at the Usak Museum weighed 23.5 grammes and the brooch it had replaced weighed 14.3, and the difference is how the substitution was proved. - The unit itself is a historical document. The Metropolitan still gives the Bryant Vase as 452 ounces 16 pennyweight in the same field as its inches, because troy weight is what a silversmith worked in and what a purchaser paid by. ## Weight is the measurement a metal object was made to carry ## The Corbridge Lanx records its own weight, and the scales nearly agree ## The Projecta Casket records its own weight, and the scales do not agree ## Three objects, three recorded weights, and what the scales say now ## A weight that has fallen is a record of polishing ## The unit survives in the museum field, and the unit is a document ## A weight that has risen is a record of a substitution ## Where weight fails, and it does fail ## How to use a weight ## Why this archive is free to read Weight is the oldest number on most metal objects and the one that gets read least, because it sits in the inscriptions field while everybody is looking at the dimensions. It was recorded in the first place because the metal was money, which means it exists for periods that recorded almost nothing else, and it was recorded precisely for the same reason. Two silver vessels in one museum show what that is worth: on one the ancient figure and the modern scale agree to within sixty-eight grammes, and on the other they are nine hundred grammes apart with nobody offering a reason. The second is the more valuable entry. Go and weigh the thing, convert the inscription yourself, publish the constant you used, and when the two numbers disagree write the disagreement down rather than choosing between them. ## Questions **Do ancient silver objects really have their weight written on them?** Some do. The British Museum records a graffito punched in dots on the base of the Corbridge Lanx reading fourteen Roman pounds, three ounces and two scruples, and a weight inscription in pointille capitals on the lid rim of the Projecta Casket reading twenty-two Roman pounds and three and a half ounces. Late Roman silver was a bullion asset and weighing it was routine. **How accurate are those ancient weights compared with a modern scale?** On the Corbridge Lanx, very. The British Museum converts the inscription to 4,668.5 grammes and weighs the dish at 4,600, a shortfall of about 68 grammes or one and a half per cent after roughly sixteen centuries. The Projecta Casket is a different story: the inscription converts to about 7,299 grammes and the casket weighs 8,200, and we could find no published explanation for the difference. **What is a pennyweight, and why do museums still use it?** A pennyweight, abbreviated dwt, is one twentieth of a troy ounce, about 1.555 grammes, named after the medieval silver penny. Museums keep it for silver because it is the unit the trade worked in: the Metropolitan gives the Bryant Vase as 452 ounces 16 pennyweight, which is 14,084.2 grammes, in the same field as the inches. **Can a weight prove that an object has been swapped?** It did at least once. When the hippocamp brooch from the Lydian Hoard on display at the Usak Museum was examined in 2006 it weighed 23.5 grammes against the original's 14.3, and that difference is what established that the piece on display was a replica. **Why does an object lose weight over time?** Mostly cleaning. Paul Revere's Sons of Liberty bowl was described in 1768 as weighing forty-five ounces and now weighs 43 ounces 16 and a half pennyweight, roughly 36 grammes less, which Jonathan Fairbanks attributes to metal lost in the original working and to two and a half centuries of polishing and wear. ## Sources - [1] British Museum, Collection Online, lanx (The Corbridge Lanx), museum number 1993,0401.1. Read for the dimensions field (Weight: 4600 grammes), the inscription transliteration and translation, the curator's arithmetic converting the inscription to 4,668.5 grammes, and the note that the graffito is punched in dots on the base near the corner of the footstand. - [2] Roman Inscriptions of Britain, RIB 2414.38, Corbridge Lanx. Independent epigraphic corpus giving the same reading, a present weight of 4,603.32 grammes, and the comment that the inscribed figures amount to 4,668 grammes, 65 grammes more than the present weight. - [3] British Museum, Collection Online, casket (The Projecta Casket), museum number 1866,1229.1. Read for the dimensions field (Weight: 8200 grammes) and for both lid-rim inscriptions, including the weight inscription XXII-III expanded as twenty-two Roman pounds, three and one-half Roman ounces. - [4] Jonathan L. Fairbanks, Paul Revere's Sons of Liberty Bowl, Colonial Society of Massachusetts. Read in the raw page for the present weight of 43 ounces 16 and a half pennyweight, the forty-five ounces of silver, the 1768 Boston notice quoting the weight and capacity, the statement that the bowl does not appear in Revere's daybooks or the family papers, and the explanation of the loss. - [5] Museum of Fine Arts, Boston, collection record for the Sons of Liberty bowl, accession 49.45. Read for the public record's dimensions, inscriptions and provenance; the published record gives no weight. - [6] Metropolitan Museum of Art Collection API, object record 1029, The Bryant Vase, accession 77.9a, b. Read for the dimensions field giving 452 oz. 16 dwt. (14084.2 g) alongside the inches and centimetres. - [7] Sharon Waxman, Chasing the Lydian Hoard, Smithsonian Magazine. Read in the raw page for the April 2006 Milliyet report, the police examination, and the sentence giving the original hippocampus at 14.3 grammes against 23.5 for the piece on display.