Is anyone familiar with a hallmark for an 18k gold case that says, "Austria/Argentina" 0.750 (in a rectangle) that would be on a Swiss wrist watch case? The watch manufacturer's name is engraved below and the hallmark is quite askew of the plane of the this mark. It seems unusual for the maker, which happens to be Girard Perregaux. I usually see different, more security-inducing, hallmarks on GP 18K cases of the '60's. The marks I see are generally well lined up with company names, etc., not slanted like the one I'm asking about. And they often have icons denoting the karats of gold as well. Any input is appreciated.