It’s a clone with the following marking.
Attached is a photo of the part.
BOBCAT WEAPONS INC, MESA AZ BM-5 9MM
I went back and looked at the piece and compared it to the part on shown in the web address, now I see what you mean by the #28. No it does not have the number 28 on it but it looks the same.
Last edited by Ozzieman; October 1, 2016 at 05:19 PM.