I have also mauser M98 8x57JS, but since I have bought drilling my M98 is on vacation. Yesterday I have bought this combinatin gun.
Any ideas of producer?

Can't tell you who finished it and put their name on it, but that action on the combo gun looks like a Ferlach gun...I'd be willing to bet.

Here's a pic of a less fancy combo gun (called a Bockbuechsflinte)...action looks very similar

Yes they are both made in Ferlach - Borovlje, for drilling one guy told me that it was made in Ferlach from one Slovenian who works there.
I will take these guns once in Ferlach and ask them there if they can tell me something about history of these rifles.

Any ideas what that M is?
Signature of producer?

http://www.singoldschuetzen.de...ff&allgsite=Beschuss

I am not sure, but a "W" often was used for
barrels with a fullchoke. "Würgebohrung"

On Slovenian hunting forum we found out that this combo gun was made by Peter Mitchelitsch in Ferlach.