AFAIK, all shoulder stock pistols over 50 years old WITH AN ORIGINAL SHOULDER STOCK have been removed from the purview of the NFA and classified as regular pistols as well as C&R. Note that being a C&R does NOT automatically remove a firearm from the NFA (a WWII Thompson SMG is a C&R, but still an NFA weapon).
I have a Mauser "red nine" (yes, original, not a Chinese fake) with an original shoulder stock. It had been registered, but when the ruling changed, I wrote BATFE specifically asking that the gun be removed from the NFRTR. I got a letter that it had been removed.
AFAIK, shoulder stock pistols newer than that, or older with a reproduction stock, are still under the NFA and must be registered.