All About Postage Stamp Trains
Power packs sold separately came in cardboard boxes having the same artwork and design as nearly all Postage Stamp products.
Aurora Postage Stamp Trains power packs came in tan with black lettering and black with white lettering; the tan packs were first, and nearly all bookshelf box sets had them. A few very rare sets had a copper-colored pack that wasn't branded for Postage Stamp Trains—possibly a pre-production unit. They were manufactured by K-F Industries in Philadelphia (founded in 1960, the company still exists, but has no website), which had an indirect connection to Aurora through Michael Tager via American Tortoise. The same packs also came with Treble-0-Lectric and Arnold Rapido sets, and likely others.
Canadian train set packs were different (below); these were made in Japan. Curiously, even though they're branded for Postage Stamp Trains, they're labeled "Model No. 4949 HO hobby transformer."
Appearing in some of the very last train sets that Aurora released were packs having a plastic top in gold or blue, with lettering heat-stamped in white (below left and center). Note the Aurora logo rendered as plain block text, a style adopted around 1973 when Aurora was bought by Nabisco. The same packs were often seen branded for Atlas, Minitrix and others.
Postage Stamp Trains is a Trademark of the Aurora Plastics Corporation.