I am trying to find step up ring or any arrangement that I can use for filters. The tread appears to be 42mm which does not match anything that I know of. First, can anyone confirm that it is actually 42mm? Second, how were filters attached to this unit - was this at one time a standard size?

Thanks John

The 8" tele-raptar for 2x3 cameras uses a series VII slip on adapter for 1-3/4 outside diameters, the same as the 162 Optars etc... I have both lenses and to use my accesories I found that if I carefully filed and sanded a slight taper on a 55mmm step up ring I was able to thread it in to the VII series enough to keep it snug. I could have filed more but wished to still use it as a 55mm also. For my purposes I use the inexpensive General brand aluminum rings.

Have fun,
Stephen