I recently bought a 440 mm 'Labor' studio portrait lens made by O.P.I. in Gand, Belgium. I have turned up he name O.P.I. in connection with binoculars and microscopes in a few eBay listings and some historica sites, and learned that was the trade name of the "Société Belge d'Optique et d'Instruments de Précision". I have only found a couple of camera-related links, and those only for ten-a-penny early C20th camera types, nothing this specialised. Does anyone know anything about O.P.I.? Any clue as to whether my lens is a derivative of other portrait types, or an oddball Belgian invention? Please excuse the double post here and at LF.info, but I wanted to catch the more European and historically-minded folk here as well as the LF-ers there.