Jim this is my honest thoughts on this.
A Winchester contract detailing 8 loops going to the Marine Corps is undeniable proof. A Marine picture that you can document to WWI, where you could count 8 loops on a case is proof it's possible. A Marine Corps letterhead document decribing a 8 loop case would also be proof. I do not think any reasonable person would argue that a 8 loop case is not Marine, if presented with one of these facts. If I was presented with this info, I would be ok cool. Yeah they did have 8 loop cases.
A typewritten name in a case that was found 80 to 100 years after it was made. I don't see that as absolute proof. Especially when you consider you only see a few of them. I see that as something of interest and it would need a lot more research. And to confirm it and say it is fact, you would need to find documentation or a photo from WWI to prove it. I think basing all your evidence on a few cases, without any documentation from WWI, leaves a lot of room for argument.
It especially raises arguments when you say that the 8 loop was the Marine contract, when the WRA docs specifically state it was a 6 loop.
I think to prove it, you need to find a document or a picture from WWI. You need something from that time period that proves it is possible the Marines had a 8 loop case.