If there was such a thing as "broders" (i.e., any unauthorized collectors' issue baseball cards) in the 1930s, these would be them.
They come to our attention via Pennsylvania collector John Rumierz, who has been sharing his lifetime collection of rare vintage baseball cards in this forum in recent months.
The cards appear to be an issue of American Boy gum, circa 1934. A cursory search of the brand on Google produced no information. I suppose it's not impossible there was a tie between the gum and the magazine by that name that was published in the 1930s, but I'd bet there isn't.
Rumierz says he bought these cards many years ago" in an old-time collection in Windsor, Ontario, Detroit's Canadian neighbor to the south. He said all of the cards in the collection were American, not Canadian. He reports he has not subsequently seen any other American Boy baseball cards.
Rumierz describes the cards as "a low-budget production" and although they are undated, he thinks they may have been issued in response to the Tigers American League pennant win in 1934 and/or their World Series title in 1935. He says they are about the size of contemporary Goudey, Diamond Stars, etc., baseball bubblegum cards, i.e., about 2-3/8" x 2-7/8".
Wording on the back of the cards indicates these were packaged with gum, probably bubblegum, and that the wrappers could be exchanged at the store for a foreign coin.
There's no indication, such as a card number, to indicate how many baseball cards may have been in the set or if, indeed, any team other than the Tigers was represented. It is also unknown whether this was a local, regional or (unlikely) national issue.
The cards were apparently unknown to Jefferson Burdick when he was compiling the American Card Catalog in the late 1930s, so there is no R-series designation for them.
John's stated purpose in sharing this information with the hobby is to solicit input from other collectors on these obscure issues. So, if you have anything to add to the conversation, please feel free to email me at firstname.lastname@example.org.