Re: advice for film holders
The standardization came later. You are right to take care about old cameras and holders.
Re: advice for film holders
If you live close to another 5x7 shooter with standard holders they may let you try one. They may just work.
I have a plate holder that although it doesn't fit properly it appears to still form a light tight seal, and I would probably only lose an edge if I used it.
Re: advice for film holders
As far as tripods go, if it is rock solid, the thread fits and it can support the weight of your camera it should work. It might look mismatched, but it should work and your photographs will neither know nor care how it matches up.
Re: advice for film holders
Is it a spring back? If so, take off the springs (i.e. unscrew the screws that hold the springs to the back frame) and lift off the ground glass frame and set it aside. Lay a ruler across the back and take a picture and post it here. I will be able to use the photo to measure the back and can then tell you if a modern firm holder will work. But I am on a trip and would not be able to measure my holders till I get back Jan. 4, but I am sure someone else here would do that for you.
Best, Tim
Re: advice for film holders
It should take a standard plate/film holders, most Seroco's do, the cameras were made specifically for Sears and Roebuck by leading manufacturers/workshops.
Ian