Are you sure on the spelling, or is it Meyer? This is the normal German spelling, pronounced Mayer...
There's quite a lot comes up under Karl Meyer on Google. Apparantly some of the Selmer Preludes came from them. My guess would be it's an Amatii stencil, if it's older, possibly East German. And Chinese if not. However I don't think it's a recognised German maker. Certainly the main German site, saxwelt.de doesn't list them as a maker.
This subject to correction: I think I've seen a couple for sale on ebay germany, and I think they were chinese stuff.
Pics would help the experts a lot. As may a serial number/makers marks.