The change in status for ALL the open bolt semi-autos came in 1982.
1986 legislation declared them to be Title II firearms...SMGs, even if they only fired semi-auto. The Open bolts manufactured from 1982-1986 have a weird standing with the NFA and I do not recall the particulars at the moment
All Open Bolt Semis manufactured prior to the 1982 administrative change are still classified as Title I firearms and transfer no differently than any other handgun
Back in the early 1980s, M11/9 SMGs were advertised at $159. The firearm cost less than the transfer tax. Oh How I long for the good old days
The open bolt M11/9 SMGs had a rate of fire between 1650 and 1850 depending on the particular firearm you measured.
I have put 10s of thousands of rounds through many examples of the M10 and M11 SMGs practicing over the decades.
Their 1600+ rate of fire is where the term "Bullet Hose" originated from, though today that term is applied to many different SMGs
The M10s were in use by small Many Agencies. Last time I looked that was still one sitting with the North Miami Beach SIU. It was right beside their Ithaca Auto Burglar...but that was several years back
I can't recall who made it but there was a shoulder holster that attached to two snaps that were mounted at the back end of the M10. The firearm hung on leather that had a swivel. You carried the 45ACP M10 on your strong side with the 12 round magazine in it while a pair of the 32 round magazines were hanging on your weak side. The firearm could be deployed very rapidly
BTW, according to Sylvia Daniels, SWD stood for Silvia & Wayne Daniels. She was a very smart business lady. I met Sylvia and Wayne back in the eighties when I used to work the semi annual Red Baron auctions