In addition to feedback from other members, you could consult “Greenberg’s Guide to Gilbert Erector Sets, Vol. 2, 1933-1962,” by William M. Bean. Though the book is out of print, it is occasionally available either from Amazon or eBay (expensive) or possibly from your local library (free). The ACGHS is currently revising and updating Bean’s guide, but this won’t likely be completed until November 2022.
David Gilbert
ACGHS Webmaster