Many german bike shops used to sell "house branded" bikes under their own label, they were reasonable bikes and typically a bit less expensive than big names. Most of these came from italy, italian frame makers were often present at german bike trade shows offering "built to your spec" deals. Biemmezeta and Billato were in that business, but also smaller, lesser known manufacturers. These sort of frames lacked the last detailing like chromed lugs or hand-filed cutouts, but had the same quality tubing. The same shops made often the not-top level bikes for big names like Colnago etc.
Some features of your frame, like the clover leaf-like lug cutout and the chromed seatstay ends, make me believe yours is one of those.