hello
I having also a Geco M 98 http://forums.nitroexpress.com/showflat.php?Cat=0&Number=138413&an=0&page=1#Post138413
Gustav Genschow & Co. AG from Karlsruhe and Berlin was one of the biggest ammunition maker in germany. it was bougth in 1963 from Dynamit Nobel. till now its the lost cost production line beside RWS. Geco had have an own factory in Suhl(what I know) but the relationship's before 1945 were very complicated there. everyone was knowing everyone, worked for everyone and in most cases was related with everyone in suhl. so its hard to say if your rifle was made from Geco. my own rifle is very similar to another 9,3x57 from Karl Bartel(Kaba).