Subcontractors make parts. Contractors make the product. Singer didn't contract, they subcontracted.
http://www.recguns.com/Sources/IIID2b1311.html
Singer made M1911A1s. they are the rarest maker. They did not make M1911s. They did not make "WWII garand rifles"
I don't mean to step on toes or call anyone out. I'd love to see a USGI Singer M1 Carbine. I don't think I'm going to though. Might see an Underwood B stamp