Have found a nice old lens of the Daguerre era which is missing its stop disk (is that the right word?). I guess these disks/plates were made from brass but I'm not sure since I have no original to compare.
Questions:
1. From which metal was the stop disk made?
2. How was the metal blackened?
3. Is there a source for the screw used to attach the plate to the lens? (the screw has a little tapered base - guess it could also be replicated by a machinist)
Here is a picture of an early achromat with a metal stop disk - at one end it is fastened to the lens with a screw, so it can open/close the lens:
(If anyone has one laying in a parts bin I would be most interested of course....)
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