I have recently come to have a set of Bausch & Lomb Protar Series VII lenses (11 3/16, 13 3/4, 16, 18 7/8, 23 1/8). I don't know if this is a complete set, of if there are other focal lengths. I am looking for information on the use of t hese lenses, as well as any practical advise anyone has. It would be really use full to find an old technical data sheet, or even catalogue information. The sp ecific information I am looking for is the effective focal length and aperature of the various combinations, angle of coverage etc.