I'm looking at a Voigtländer Heliar 21cm f/4.5 for use with my Sinar F2 5x7 camera. The lens is a barrel type so it's not mounted in a shutter. Looks pretty straightforward. A bit like an SLR lens but with a thread at the rear instead of a bayonet. Apparently this is not uncommon for this lens. Can this mounted on a Sinar DB board for use with a Sinar auto aperture shutter? Would anyone know which lens board would fit the thread on the lens? I have looked around but found no specification of the thread.