More input could be obtained from Proof House in Ferlach:

Beschussamt Ferlach
Maschinengasse 3-4
A-9170 Ferlach
Austria
Phone: (0)4227 2576
Fax: (0)4227 4174
E-mail: beschussamt_ferlach@aon.at

You could send them photos but I think these numbers are essential:
Hammer gun:
action: 1699.1700.14
barrels: 11039.14
Hammerless:
action: 2415.35
barrels: 1441.35

I would imagine they have these guns recorded in their old books and should be able to look up for you some additional information including who subjected them for proof: Ecker, one of the Ferlach gunmakers, or maybe even a third party.

With kind regards,
Jani