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:
3151------old diaph scale----Jacques collec
6438------old diaph scale----eBay.
8892------?----------------------- eBay
90350----old diaph scale-----eBay.