Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I have found an old post from Mike (Maxwell) stating:

So, no one has a catalog picture for the double slide valve below? but we have pictures of the single slide valve/rod from the 1929 catalog below. I believe that the single slide valve/rod was produced before the double; do you agree?

Mine is the single, but he said 1929 catalog, so maybe you are close on the date Scott?