Wet plate holders

[andrewch59]

I have just restored a camera I bought as a box of kindling from someone.
The camera now sits proud and shiny but minus bellows. In amongst the kindling were two plate holders with CV O VC etched into the side of the holder, with corresponding holes drilled into frame. I know it is probably for aligning the different size inserts for plates. ie.. C for cabinet.
Can anyone shed some light on these? Maker or what sizes they stand for?
153573153574

[Steven Tribe]

Plate holder which fits on a sliding back. O position uses the FULL plate (dry or wet) inserted. CV uses just the left-hand half of the plate and VC uses the right-hand side afterwards. So two exposures on one plate. THe selection of C or V may different spacing. Measure up!