20-years ago I bought my first 4x5 from a studio that was going out of business It came with a lens that's labeled Rodenstock Sironar 1: 5.6 f=210mm - plain Sironar, no S or N or Apo. I've used it for all these years without paying a lot of attention to it.

A few weeks ago, I got my first 8x10. According to everything I see on the net, the Rodenstock has only a 266mm coverage circle, not enough for 8x10, but I thought I'd try it anyway.

I made a temporary lens board and stuck the lens on the 8x10 - I was stunned to see it covers with plenty of movement. Then I looked more closely at the lens and see f-stops engraved not only for 210mm but also 400mm. Sure enough, removing the front element focuses at about 400mm.

I wonder if I have something other than a plain Sironar. Any ideas?
juan