Winchester magazine question

I have a Winchester UW magazine made by Union Hardware, flat bottom Type II. It's in new condition with oil paper. Is this a common magazine or not?

Yes, it is a fairly common mag. Be careful about that wrapping. It is not an original wrapper. There is a good possibility of rust forming under it. I've seen that many times. People think they have a pristine mag and open it up to find heavy rust and terrible pitting.

I opened it up and it still has cosmo on it....Looks AOK

Glad to hear it. It seen far too many that were badly rusted.