Those yellow things are slip blocks that are put under wheels to prevent them from moving (I don't have a better picture but it is visible there -
https://lh6.googleusercontent.com/-ZOac ... GP6936.JPG). They have nothing to do with de/rerailing.
Anyway, Mark, if you haven't already been to Railway Museum in Luzna u Rakovnika, you should definitely go there. Also if you'd like to visit some railway modeling stores in Prague, just drop me a PM and I'll write down a list of them + give you directions how to get there. Too bad swapmeets don't take place during summer holidays, there would be much more to see and buy. Unfortunately the next one is in September.