Here we have a Gundlach Optical Company RR lens that has a 12 inch FL f7 and using the rear cell only converts to a 600mm lens. It is an early lens, serial number 687. The glass is clean for its age, but has slight delamination (correct term?) separation which would not adversely effect it images. It has a nonoriginal brass flange that fits and comes with one of its original stop which is marked "32". How about $225 plus shipping/insurance/ and 3% paypal fees if you pay in that manner. 3% of purchase price to APUG. Email or pm me with questions etc. Thanks. Jon