what's this thing?

[DrTang]

Picked up a brass lens off craigslist.. un named or marked at all

it did, however come with a rear accessory 'diopter' ? or lens element that slips on

I haven't mounted it but it seems to increase focal length when on


anyone seen anything like that?


note: the white gunk in the second pix is teflon tape from a not quite right flange



127950 127951

[Steven Tribe]

There were varieties of Projection lenses that were sold with alternative lenses that changed the effective focal length. Most of these had the usual large text "8 in", "10 in" stamped on the side. I think that this is the purpose of the lens, although, usually , there was a complete cell that should be swapped.

[DrTang]

Thanks

I figured it was something like that