While certainly not 100% by any means, in many cases one can simply make an initial determination just by eyeballing it. Once you've viewed a lot of German work done in whatever walnut they were using, and compare it to genuine earlier American work in walnut (eastern walnut, not talking about transplanted or grafted west coast stuff) you can at the least get an initial gut feel. There generally is an observable difference, at least in my opinion/experience. I'd not try to use such an eyeball test via photos only, however, as it's probably an exercise in futility. Just going by these good color photos, I can kind of see it going either way! Which offers no help, I know. Anyway the more I look at this little sucker, the more I like it regardless.
I don't think the guy that carved this rifle was used to carving many arms. The stock work is very competent, and the metal work likewise is quite nice. I don't see the carved decoration as meeting the same standard of training, although I don't in any way mean that as a derogatory statement. George noted the same thing. Whether it means anything, I have no idea.