This is a legendary Zeiss Jena f6.3 6-1/2" lens (165mm) with both elements in place. Front group is #58794 and rear is #58797
It has a bayonet type quick release for whatever old press camera it came on. The front element comes out with 1/3rd turn.
With just the rear element on place it is 11-1/4 inches, 285mm.
This is the European version, Carl Zeiss built Protar VIIa. Covers 5X7 combined and the 285 element covers 8X10 easily. Glass is excellent with just a bit of edge seperation seen on one end. No hindrance optically. $155USD
Price : 155.00