msalm
If you have the reamer in hand you should be able to come close to an ID of the parent case. Most likely the basic 308W but the designer could have specified many cases as parent. 308, 300 SAV, 250 SAV, 22-250, etc. The reamer print could specify the particular case that he had in mind or it may not say anything at all.
It could be based on one of the fat cases also. A few simple measurements would tell you.
UPDATE - I just noted a wildcat in my collection called the 6.5 Rogue. Based on the WSM case. Maybe there's a clue there???
Ray