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That is the latest Schneider 40/3.5 lens, fully compatible. It happens to be quite small in size, and a good lens. I have one for my 6003. Fully recommended. There was a Zeiss 40 mm, I think both a FLE one and not. The earlier one (not FLT) was quite big. But others may know more. At one time, both the Schneider and Zeiss were in the Rollei brochure at the same time!
Both the Schneider 40mm 3.5 and the Zeiss 4.0 Distagon FLE lenses are good performers. The Schneider is a bit more compact, and has overall higher resolution from 3.5 to 5.6 than the Zeiss Distagon. From 5.6 to 8.0, the Zeiss version has better overall resolution and performance from center to the edge. My personal opinion is that the adjustable floating elements of the Zeiss version provides better correction at close distances. The Zeiss version lens designated as FLE is basically the same 40mm lens that the NASA space program used on the moon.
All in all, both the Schneider 40 and Zeiss 40 FLE are very good lenses. Unless you're printing larger than 20"x 20", you probably wouldn't see much difference between these two lenses.
A new Schneider 40mm 3.5 Super Angulon lens goes for around $3800.00 in the US. A used one in mint condition would probably go for around $2500.00 - $3000.00.