1936 Zeiss Ikon

Appears to have perfect perspective (verticals). Is that due to post processing (i.e. Photoshop) or thanks to viewfinder being better than it seemed?

Looks plenty contrasty to me.

Should be the 510/2 with the optical indirect vision viewfinder on the lens (image is very reduced in size) ... ?
Using the second viewfinder frame on body one have to go quite close to get the image correct.
IIRC there was an additional magnifier attachment (5x) for the optical viewfinder.
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I like your image - the old 3-element Nettar is not that bad as often reported. It renders beautifully.

Actually quite an impressive result for something from the 1930s!
(This comment from someone whose first digi-thing died in ten years!!! )

Yes -- it IS 1936 510/2 engraved in the black covering near back door latch. I did not have to correct verticals for THIS one.

@pentaxpete You have a steady hand