I have about 35 to 40 original 30 rounders and about 12 different fakes. Comparison, which I will not reveal shows there are characteristics on each original maker. I cannot let the information out because the fakers will adopt the changes.
As far as B Jahn, I have studied the contract and there was no unmarked contract. I have an unmarked J Jahn and SEY, but I suspect they were small production errors, or possibly foreign purchases. I know their ID due to their characteristics.
I have seen several hundred new in wrap magazines over the years and years ago they were opened at gun shows in order to sell them (all rewraps for inspection and repack). None were ever unmarked.