To answer questions,... it ,... they are 315S with a little plate on the back for switching impedence,.... they were purchased,.... not found, along with an ampex tape deck from a guy who recorded school bands, and choirs with that set-up...
I did also find a couple of other shure mics,...(yes in 'that' house,.... ) .
They are a model that my buddy at the music store could not find in his reference book, so maybe someone here can help,... model 535, with a switch right on it that is the off/H/L impedence.... looks to me like it is maybe from the late 50s, early 60s,.... and a omnidirectional, maybe a pre 57,...???