Personally, I have always been uncomfortable using the term for two reasons. First of all, I studied Latin and celo (-are, -avi, -atum) means to hide or to conceal or to keep someone ignorant of something, and thus it stands to reason that celator would mean one who hides or conceals or someone who is keeping something from someone. I finally remembered to look up "celator" in the Oxford Latin Dictionary today which it, in fact, defines as someone who conceals. Secondly, having done some research on mint organization in Rome several years ago, I discovered that another term, signator, might have been used in Roman antiquity to describe die-engravers.
The collector magazine the Celator explains the term is an anglicized form of caelator, which does in fact mean an engraver or someone who works in bas-relief. A search through the Thesaurus Linguae Latinae, however, does not appear to reveal any ancient contexts in which it was used specifically referencing the engraving of coin dies.
Unfortunately, much of our studies about minting activity and organization in ancient Rome have to be extrapolated from the study of the coins themselves and what few scant other sources remain. No literary texts survive telling us about mint officials and how they were named or organized, but we may know the location of the post-c. AD 80 mint (before it was housed in the Temple of Juno Moneta), which is often said to be the building now below the Church of San Clemente (e.g. Coarelli, F. 1993-2000, “Moneta, M. Caesaris,” in Steinby, M. (ed.) Lexicon Topographicum Urbis Romae. vol III. 280f. (Rome: Quasar)). One of the reasons why this building is postulated as the post-c. AD 80 mint is that some Trajanic inscriptions were found in the area naming some mint officials and workers (CIL vi, 42-44, 239, 791). RIC I² (pp. 14-15) has a good summary of the inscriptions and an interpretation of the "job titles" that are listed. Those that are named are:
- optio et exactor auri argenti et aeris (CIL vi, 42-44, 239, 791) - a director or official in charge of minting; there was second optio, whom the authors of the revised RIC I believed to have been an assistant of some sort (RIC I², p. 14)
- officinatores - those in charge of each individual officina or workshop (CIL vi, 43
- signatores - die-engravers (CIL vi, 44)
- suppostores - those who would have placed the flans on the anvil for striking (CIL vi, 44)
- malleatores - hammer men or strikers (CIL vi, 44)
- conductores flaturae - metal-melters or metal-refiners, perhaps the flan casters (CIL vi, 791)
Even the Oxford Latin Dictionary suggests that signator may have been the term used to reference a type of mint worker. Signator derives from signo (-are, -avi, -atum), which means to bear witness to the signing of a document, a process which in Roman times would have involved sealing. Sigillum, another related word, means seal. The striking of coinage provides an official "seal" on a planchet of metal making it official currency of the state. The term signator makes logical sense to have been a word commonly used to refer to a Roman coin die-engraver, a "sealer" in a sense. It also is the only word used for a die-engraver that can be corroborated by surviving evidence.
In scholarly literature, I recall having only seen "die-engraver" used to describe ancient die-engravers and perhaps this is the simplest way to go about referring to these people. If a Latin term is to be insisted upon, I would prefer signator since it is the only term used for a die-engraver for which we have ancient evidence, coming from the above-discussed Trajanic inscriptions. Caelator is a somewhat accurate term in that it means "engraver," someone who could have worked in all sorts of metalwork, but this is a more generalized term and one for which we do not have direct evidence that suggests it would have conveyed "die-engraver" in the same way that signator would have. Celator is a corrupted form of caelator frequently used by ancient coin enthusiasts. Indeed, many other numismatic terms have been anglicized such as sestertius, which is sometimes called a "sesterce." The problem with using celator in lieu of caelator, however, is that celator is also Latin word that has a very different meaning. Of all the potential Latin terms to use signator would be the most precise and accurate. I think I am going to stick to "die-engraver" though.
(Plan of the structure beneath S. Clemente (After Claridge 1998. Rome: An Oxford Archaeological Guide. (Oxford: Oxford University Press), 285).