The 1937 Colt Electrical Products catalog does not list any breaker panelboards. They do list "auxiliary" freestanding circuit breakers. This catalog, especially the section on cast iron service and fuse boxes brought back some memories, some terrifying, of eliminating the remaining downtown Milwaukee, WI 250 & 600 volt DC systems in the early 70's.
I'm in the process of moving and was going to dump this catalog. If anyone wants it let me know, no charge, I'll pay the postage, as I hate to dump what someone may want. Ping @ midlf@execpc.com. This catalog was on its way out the door at WEPCo in the mid 70's and it was too interesting to let the trash man have it.
MIDLF
