I think I understand the procedure as described in the last post, but I'm also beginning to believe that what I purchased is not 100% Gaoersi. The body has the name in several places, so I'm good there. The next piece, rectangular, about 1" thick, mounts up to the body with 4 thumb screws and must also be Gaoersi.(?) However, the next two pieces (lens cone? and focusing ring) could be another brand? These last two connect to the first via a threaded 85mm hole. Is this hole common to other cameras? If so, could a previous owner have swapped components? Again, I am unsure how much interchangeability there is among these fixed mount cameras. Maybe I need to figure out where to post some pictures and give better clues. Thanks again for the collective insight.