Corbin 4 x 5 Synchro Lens

[William Francis Ahearn]

I recently inherited some 4 x 5 equipment which included three lens boards for a Toyo 4 x 5 View Camera. One is a blank board, One looks like a lens extender, and the third Has a Corbin Synchro lens. Does anyone know about the Corbin Synchro Lens and how it is used? It is made of brass. There is no glass. There are three letters engraved on the brass rim that adjusts "T" "B" "1" There is a shutter cock and a place for a cable release to control the aperture
It seems like it might be a mechanical shutter to be used with a lens that has no shutter. Something I have not seen before. I have photos if any one cares to see them.
Any help you can offer? Is it valuable? Thanks. Bill

[Glenn Thoreson]

The letters stand for Time, Bulb and Instant, which is probably somewhere in the 1/25 of a second range. If it has a built in aperture iris it was made for a particular lens, which you say is missing. Valuable? Probably not. A picture or two would help, though.