Mike(Texasjack),
I guess others have answered most of your questions, or will,but the following are a couple that may have been missed. The trigger guard is not bone, rather it is horn(buffalo)as is the butt plate.The gun hasn't been rechambered, it was always intended for 7x57R.If it had been rechambered or had any other significant work,it would have a crown "R"(repair)proof.Merkel may not address your questions about the scope, they didn't make it and likely didn't mount it.Members of this board or German Gun Collectors Assn.board can help with adjusting it.BTW if you are interested in German guns,you might consider joining the GGCA.
Mike