Vintage 1950s Novelty Alka-Seltzer Powered Miniature Toy Boats

A novelty item (well, items) from the 1950s which would probably have been a pocket-money toy, possibly even bought from a vending machine, these are a pair of alka-seltzer powered miniature toy boats. There’s not much more to be said about them really, except that presumably they still work as per the instructions provided.