I have these three plate cameras that I traded with a Dutch Sergeant at Sheppard AFB back in the 80's. They seem to be w/o name except on the lenses. One of the larger ones has the name "HELFIX" on the bed but I can't get that to correspond to a brand name. One of the larger has an unmarked plate holder. The plate holder and the ground glass seem to interchange between the larger cameras. W/o a brand name I don't know what to look for in more plate holders. Should I be looking for plate holders based on measurements and style?

I think I might find a roll film holder for the smaller.