Re: USMC scopes
No telling how many of the 8541 scopes are out there, but I am sure it is more than 12. He maybe talking about the early scopes that also said Premier on the side, I believe these were early test scopes.
As for the 8x Unertls, there were about 1775 made. Many did not survive WW2, the ones that did went on to serve in Korea and Vietnam. I have seen quite a few in public hands and they run about $5K with the can. These scopes usually have the recoil spring missing. Beware of fakes, they are out there.
The green Redfields (accurange) from the M40 are also pretty scarce, there was approx 800 made, many did not survive the jungle. Not sure how many are owned by collectors (<50 would be my guess), the USMC never surplused these scopes to the public. I have come across 4 or 5 in 25 years of collecting, only 2 of those were for sale.
As for the Leupold 10X for the M40, I have never seen one or heard of them being used. The original USMC contract called for the rifles to be delivered from Remington with the Redfields and I can see no reason why Remington would have not done that. Not saying its not true because I am not sure, just never seen the data.
The later 10X Unertl was also never surplused and there are very few (as in less than 20) legally owned by civilians. A few went to the FBI and may be floating around but they are hard to come by. Paperwork showing the release from the military is essential if you come across one for sale.