Topcor/Horseman 75mm Lensboard Swap...

This started as a 75mm Topcor/Horseman Lensboard swap. As Horseman 6x9cm owners know, they upgraded the lens line at one point by making some of the lensboards recessed. This, of course, affects where the infinity stops need to be to focus with the rangefinder.

The change in lensboards is evident by the paint on the lensboard. The older flat lensboards have a flat hammered finish. The recessed lensboards have a wrinkle black finish.

The issue at hand is that the 65mm and 75mm lenses need to share an infinity stop. So, if you have, for example, a newer 65mm and an older 75mm there will be issues. This was my situation.

So, I looked for a 75mm lens with bad elements or bad shutter, in which I could swap my flat lensboard for the recessed one. I wound up finding an inexpensive 75mm with foggy lens elements.

Once my lens arrived, I saw some subtle differences with the Seiko shutters. Notice the different shutter cocking levers and the different focus levers. Looked like the lensboard swap might be difficult. So I tried swapping the foggy lens cells on the recessed lensboard with the clear lens cells in the flat lensboard.

Turns out this could not be done as the different Seiko shutters have different lens cell mounting threads.

Next step is to replaced the glass elements in each of the lens cells. I did this successfully with a Caltar to Topcor swap for a foggy Horseman 4x5" 90mm lens a while back (notice the different rear housings; the Caltar has the same glass but does not fit the Horseman FA.)

Good news is that after removing the glass elements from the Topcor/Horseman 75mm lens on the recessed lensboard, the glass cleaned up just fine. In fact the new lens elements are clearer than my existing 75mm.
So, I put everything back together and now I can use my this new 75mm lens with my rangefinder!