Intended to be used with FED cameras. Normal lens in normal mount but with different engravings. Used with a proper tube the engravings give the relationship between image size and object . Used for document and object reproduction .
Known serial numbers:
##2492 _____ new diaphragm scale ____ eBay
##3151 _____ old diaphragm scale _____ Jacques coll.
##6438 _____ old diaphragm scale _____ eBay
##8748 _____ old diaphragm scale _____ seen on SovietCams
##8892 _____ ? ____________________ eBay
#90350 _____ old diaphragm scale _____ eBay