Truth be told, there is no truly satisfactory free-bee resource on the Internet for prewar AF.
The HSL disks and Doyle's book are both worthy suggestions. The HSL disks (American Flyer "Chicago Era" Digital Archive 1907 to 1937 and the A. C. Gilbert Digital Archive 1937-45) cover all of the catalogs from 1907 to 1942 plus other goodies beyond what one will find on the Internet. Doyle's book is worth having for the pictures, however, please beware that the Doyle AF book has a fair number of errors, omissions, etc. And, its major emphasis is on postwar S gauge.
It won't be cheap because it is out of print, but the best single book to own for prewar AF O gauge is the REVISED edition of Alan Schuweiler's Greenberg Guide to American Flyer Prewar O gauge (1997). This is the superior resource to own if one is going to get serious about prewar O gauge Flyer.
You will find that picking up old copies of "The Collector" is rewarding. "The Collector" was the publication of the American Flyer Collectors Club published and edited by Frank C. Hare back in the day. The Toy Train Museum has a complete set (~84 issues), I believe.
Hope this is of some help.
Bob
