Lucky guess to my unknown lens

[JMC1969]

A while ago. I posted a classifieds ad to sell a Rochester-optical I picked up and cleaned up.
(there was a url link here which no longer exists)

The lens on it was something I was unfamiliar with and I assumed was a junk lens until a response to the ad. Camera parts did not sell and i got interested in this lens. Last night I had a bit of inspiration, though a week and a half ago I built a lens board to hold this lens. No idea what f-stop to shoot this at, though I measured the lens to be roughly 334mm. I cut a piece of cardboard from a 12 pack box to use as a "old hat", had a sheet of very old, non-refrigerated polaroid type 59 color and took this shoot on a guess. 20 secs exposure. no idea what this actually tells me, but it was nice to get a exposure on a first try and I am happy with the craziness of the print.

 

[Christopher Walrath]

Based on the first image and your focal length, I would say that your wide open is around f/5.6 or so. I presume no aperture or identifying markings as you mention none. I would have liked a side shot of the lens for guessing. But I do love the combination of old instant film and the mystery lens. Neat.

 

[JMC1969]

Thank you for the response Chris. Here is the side view. The only markings are the straight line etched seen in this photo and the roman numeral IV in the backside. The line and the number are not in-line with each other.

A little more info, This was my first and only experience with Polaroid type 59. It is rated at 80asa. Moments before, I had shot a sheet of type 55 rated at 50asa, but I always shoot it at 25. I had a meter reading for that shot of 30sec @ f6.3. Had I used the same method and shot the Type 59 at half the stated asa (ie 40) that would have given me 20sec @ f5.6 according to simply moving the asa dial on my Luna-pro. So I would say you had a pretty good guess at this as well. Yours may have been more educated than mine of course, being that mine was more like grabbing a number out of the sky.