I found an instruction sheet on it. The called it an Estar AH base, whatever that is. But I do remember it having a different feel about it.. It was clear and had no anti-light piping dye in it.,like regular Kodak film. Seems like it might have been a bit thinner too, but I can't be sure of that. Not sure if it pertains to the OP's question, other than he said 120 film, which is thinner than 35mm, as far as I ever knew. All film is made in rolls. The people whose film came from the outer layers of the master roll naturally go flatter film than the ones who got the inner layers. Maybe he was just unlucky and got a roll cut from the first layer.