These are the marks that were used on foreign made arms and barrels at the proof house in St. Etienne.

[Linked Image from i.ibb.co]
[Linked Image from i.ibb.co]

The block letter stamp came into use after 1923. The other one, with just the AE, dates to 1879, or so.

I’m not positive when use of either version ended.

Best,
Ted