Hi there,
I've got almost the same bike, a Wheeler 3000 Cross Line, but with Shimano Exage 300 LX group (maybe older end 80's, start 90's). The frame is Tange MTB Cr-Mo P.G. and the fork Tange MTB Cro-Moly "Response Fork".
The brand seems to be from Switzerland, still alive. I didn't find any informations about those (our) bikes so far but I still try to.
Let's keep in touch.