If they’re tricky to produce well, that suggests another possibility - maybe they were a journeyman piece for bronze crafters. Does it require combining a number of different techniques to produce? Would deficiencies in particular techniques manifest in obvious flaws in the finished artifact?

Or maybe they’re more like fizzbuzz for gallo-Roman bronze artificers. You show up at an interview and they ask you to knock out one of these to prove you’re not an idiot.