The old Austro – Hungarian proof law was to protect the domestic market of that empire only. All guns to be sold within the empire had to pass an Austrian proofhouse, regardless of having been already proofed somewhere else. There was no mutual acceptance of foreign proofs. So Austrian guns made for export were most often not proofed in Austria, as they had to be proofed elsewhere anyhow.Many Weipert, Bohemia, then A-H, sporting guns Show no Weipert proofhouse marks. They were carried across the border (just a few hundred yards) and proofed by the German Zella-Mehlis proofhouse. Military firearms were not civilian proofed. The Steyr factory sold many such military production Mannlichers and Mannlicher – Schoenauers through Belgian and British international arms dealers like Le Personne to anyone asking. Most pre-WW1 British Mannlichers and Mannlicher – Schoenauers I have seen started life as such military rifles, sporterised to several grades, resighted and restocked by British gunmakers like George Gibbs in Bristol or the Birmingham guntrade.
Afaik those circle-T and circle-V marks are Steyr factory internal quality control marks, found on all export military rifles. The explanation “Tiegelgusstahl” is sort of an urban legend.
BTW, there is an easy way to distinguish a civilian Mannlicher - Schoenauer receiver from a military production one, apart from inscriptions: The commercial ones have a bolt hold down spring mounted in the right side of the receiver ring, just behind the bolt handle. Military production receivers lack this device.