DGM, thanks for that info! Didn't think to look in trade magazines.
I just remembered that Steve Stanchfield did
a post on this film on Cartoon Research's Thunderbean Thursday three years back, and he sets it at 1934. Paging Steve Stanchfield...
I do have a bit of strange speculation regarding the release date, though. Remember, this theory has absolutely no evidence, so don't post it on Wikipedia.
I have a theory that the 1948 release date was a date when it was released to the home movie market, similar to how the Harman-Ising Cubby Bear cartoon "Mischevious Mice" was produce in 1933, shelved, and released around 1947 to the home movie market.