I picked this up at a yard sale a few years ago for $10.00 and am wondering if it's complete? The lens is different from what I'm accustomed to, it consists of front element, aperture, and rear element and screws entirely into the front of the shutter. I'm accustomed to lenses which have a front element that screws into the front of the shutter, and a rear element that screws into the rear of the shutter, e.g. a Copal, which also traditionally contains the aperture. The MP-4 is pretty cool in that it is self cocking, but it doesn't have an aperture, in addition to Polaroid MP-4, it is also marked Copal (Made in Japan). It does have threads in the rear (but nothing is screwed in there).