Carl Zeiss J.R. Tessar 500mm f5?

[monkeymon]

Hello

I got this Carl Zeiss Jena J.R. Tessar 500mm f/5 lens. Just noticed, that it's marked J.R. Tessar. Not just plain Tessar as my other Zeiss Tessars lenses. It's marked with red T for coating.

Anyone know what the J.R. stands for?

One cool thing about this lens is, that i can unscrew the first element. In my other (f3.5) tessars, the two front elements unscrew as a block. Doesn't this means i can use the front lens as a soft focus control device?

[Dan Fromm]

Serial number?

[Steven Tribe]

Engraved JR is really IR!

Post-war may be different, though.

[monkeymon]

http://tempppz.host-ed.me/temp/tessar500_1.jpg

http://tempppz.host-ed.me/temp/tessar500_2.jpg

Here is couple of pictures of it, another weird thing is the F stop scale on the barrel. Starts from f/3.5... i own a 300/3.5 Tessar, but it's not as big as this lens. I there bigger f3.5 tessars out there?

It's missing the aperture control wheel, but the aperture is present, probably removed from some sort of heavy aerial camera where the aperture controls have been linked

[Dan Fromm]

Probably made in 1939. Probably an aerial camera lens, as you suggest. And could well be, as Steven suggests, optimized for I.R.