Hey guys, I'm new to the forums. I've been wanting to get into medium format for a while, and coincidentally just discovered a Pocket Kodak in the spare room closet. I've gone over it and it looks to function properly and is light tight. My main question is how I'll know when I've advanced the film enough after taking a shot. There is a window in the rear cover that originally had red plastic over it, but the plastic is long gone and I've taped it over. I understand that 120 has backing paper...can I just pull the tape up for a short period and advance till I see the next frame number? How do I know that it's the correct frame number for a 6x9 neg?