Wow lovely rifle.Definitely a product of Schul marketed in India by Mantons. The 405 was popular in India more as a lever action round though some doubles were also sold. The famous hunter of Man eating Tigers Kenneth Anderson used a lever action 405. Incidentally German markings are based on a go, no go gauge. The 10mm is not the Groove/land diameter but the diameter of the largest gauge that would enter the barrel. Therefore the bore would be anything between 10 --10.1 mm plus the groove depth.