I have a 1903 Red Star and 1941 M1 Lend Lease and love the history that goes with it. My Red star is the easiest to prove it was a LL as there are around 200 of them and their serial numbers are known. The Garand is tougher but I am as certain as you can be that mine is a LL.
I don't yet know the history of Thompson style guns like you have listed being lend leases, which is why I asked the question. I know with M1 Garands, Brittish proofs aren't enough to prove it was an actual lend lease. Maybe they are with this gun? I have no idea. I am a Lend Lease collector and was simply curious about your listing. It is a beautiful gun and someone would be lucky to have it. Good luck with your sale