Larry,
A European Gun Encyclopedia makes much the same report, and rates one of the four Arizagas as a top-level maker of bespoke guns. The Dakin Arizagas appear to have an unattractive record. However, it is pretty likely that one could buy a similarly marked Union Armera with confidence. The O'Connor reference is frequently cited in the literature, and again,the question is 'which Armera?" or even 'When was it which Armera?'.
In this case, even after a bit of research and verifying the ID of stamps I don't know, it'll prob'ly still come down to the old 'buy the gun, not the name'.
Thanks for your contribution to the quest,
John
