I was looking @ the rear cell on my B&L lens, and it's 23 1/4" f/l. The front cell is 18 7/8" f/l. The old B&L table never put a longer cell in the rear. http://www.cameraeccentric.com/html/info/bauschlomb_3.html I got the camera from the original family owner, and it was apparently ordered this way in 1923. Makes me wonder ... any thoughts on this anomaly?