ust inherited this camera from my grandfather and I've already asked this question and been told that its a fixed lens camera and that you just screw the lenses on to the fixed lens, but the lenses I have, which I am certain are for the Contina, wont simply screw on to it. Please, someone with a Contina or experience with one help me out. TELL ME HOW TO DO IT IN DETAIL. Is their some kind of adapter for it???

I am not sure exactly what model it is but it looks like a contina IIa but it doesn't have a dial in the middle in top, but rather one at each side and it has a square viewfinder. I also have a model that is nearly exactly the same except the lens is a little bit different and the viewfinder is circular. The screw that the external lenses have are not typical screws, I'm not sure how to describe it but they have three slope.
I believe it was purchased in Mexico if that matters