Actually they have a couple Shure dynamics (radioshack.com) that are not
rebadged at all. I wonder what the same mics are called in the Shure product
line?

I think they are from Shure's PG series of mics. I don't know this
for a fact, but I suspect the PG's use cartridges designed for the SM
series that didn't quite meet spec. but not actually bad.
If you go with RS's higher priced mics, you will probably be pleased
with them
(for cheap mics.).

Lee Salter