Here is the PAS identification (with my comments below):
"Romano-British"I appreciate that PAS staff have a large workload and I hate to nitpick but artefacts of this type are very well known (Kennedy Type 20) and extensively recorded in the literature. More worryingly, although they are common on the modern antiquities market, it is extremely unlikely that they ever formed part of Britain's ancient archaeology.
It has nothing to do with Romano-British culture.
"known as a 'factory lamp' or firmalampe"
It does not even remotely resemble that type of lamp.
"Probably made in Gaul or Germany."
It was made in northern Syria, at the opposite end of the Roman Empire.
"2nd or 3rd century."
It is not earlier than the 5th to 6th centuries AD.
The PAS identification (a 'factory lamp' made in Gaul during the 2nd century) fits plausibly into Romano-British archaeology. The reality is far more doubtful.
The difficulty here seems to be that the identification of the object was an unwarranted assumption, guided by the narrow confines of what would be expected within a supposed British context and tailoring it to fit, rather than accepting that the discovery of the object was very different to that of a documented excavation and that the object could not safely be treated in the same way. Familiarity with a much wider international typology than that of Wheeler's localised (and long outdated!) London in Roman Times was called for. The episode highlights the importance of recognising that PAS recording is not a substitute for traditional archaeology.
I once mentioned that PAS records are inherently open to abuse and are thus unreliable. A careless and incorrect identification compounds the problem. It is misleading and potentially distorts our perception of the British past. Moreover, it lends credibility to nonsense invented to exploit that misperception.