Creative Merchandisers were a Chicago-based promotional company who often flirted with the idea of re-using Letraset products for products in the US, for which they coined the trademark "Rub-a-Doodles". These two are examples that actually made it to press.
For "Time Machine", Letraset were commissioned to produce an original set of transfers.

In 1902 Buster Keaton was a popular child actor on the stage when Richard F. Outcault created the character named after him. The newspaper strip was immensely popular, & just two years later the Brown Shoe Company paid for a license to use the character as their mascot. Sixty-six more years, & here we are…

The other Buster Brown set is a straightforward reprint of Peter Archer's Red Action Transfers set, Hunting Tigers.

Picture Credit: The SPLAT Scan Archives