The 450 is part of the pack film series from the late 60's to 70's that includes models from 100 thru 450. That 100 not to be confused with an earlier 50's era roll film model. I believe all in this series take the pack film with 3.25x4.25 image size. This includes 669, 690, 667 and 664. A number of others as well. I think Polaroids web site covers that fairly well under "peel apart" pack films. They sell some of them on line, but not all, I don't think.