Looking for some guidance, I'm talking with a non Model T Guy who acquired some parts as part of another deal.
If you had transmissions, don't know where they came from or why they are no longer mounted to an engine but you can look for obvious cracks in the drums, what else would you look for? these are all mounted to a flywheel with magnets.
What is the high and low value to re-sell?
At auctions I've bought engines with transmissions attached from $5 to $65. Whether parts are usable is a crapshoot. Often you don't know if drums are cracked until you sandblast them. Most reverse drums are no good.
The obvious cracks you can see the ones we mostly find are in the web and not the band contact surface. At the first of the year after going through a 100 plus drums and saving a few good gears, I scrap them. Your mileage maybe different
Ben, a few things to consider. Just one good drum will be worth around $100 minus your work to get to it. As Steve points out, reverse drums are at a premium, but you won't know how good they are until you strip them out. Wide brake drums from 26-7 transmissions are desirable, because they will have the hardened lug shoes for the clutch plates. These drums can be used in earlier cars with modification.
You should be able to see the triple gears. Check for wear on the teeth. If worn, the driven gear is likely the same.
The trans in my 1917 shooting brake came out of a 1920 closed motor that I paid $100 for. It is like new, excellent drums, no bushing wear, virgin ring gear etc. I just balanced it and run it as found. The best trans I have ever driven. If you find one like it, it would be worth hundreds, but you won't know until you strip it.
Hope this is some help.
Allan from down under.