spiral-back freight wheels

About when was the transition period from mostly these to mostly
smooth-back on cars being delivered and/or rebuilt?

Hal

Scroll down on thie link and you will find all the info you need…
http://www.modelrailroader.com/Content/Dynamic/Articles/000/000/002/197xvpbs.asp

I am anxious to see how many times the same info will be posted in different wording.

Thanks, csmith. That was what I needed, and actually was pretty
close to what I guessed.

Hal