The set (which Engel catalogues as JGA 11) contains 48 cards and was originally sold as a set that came in a very cute little box. I bought this set a few years ago, before the pandemic boom caused prices to rise. They used to sometimes show up on Yahoo Auctions but its been a long time since I saw one. The box is notable for the hamfisted attempt to spell baseball cards in English on the side:
The set is somewhat rare (Engel rates it R1) and is popular for having Wally Yonanime's rookie card in it:
I had always though this set was only sold in those cute "base boll card" boxes, and Engel indicates as much in his description of the set as well. But last week an interesting item sold (for 62,000 Yen, unfortunately too much for my budget) on Yahoo Auctions. It was a taba of 120 baseball cards. Taba are little envelopes, each containing one card, that were bundled together with a string. Anyone wanting to buy a card could simply pull a taba off of the string. It was a common way for cards to be sold in Japan from the 1950s until as recently as the 1990s.
What caught my eye about this taba was that it had a card from the 1951 Osamu Gangu set on the front of it.It seems that each of the taba in this one had a card from the Osato Gangu set in it, with four prize cards (redeemable for something, not sure what in the case of these) and the rest being regular cards.
Since the Osato Gangu cards were a game that was meant to be played as a set (it comes with instructions, though I have to admit I haven't read them and have no idea how to play), I suspect that these taba weren't created by the original maker of the cards but rather by a third party who might have gotten their hands on some unsold "dead stock" of them or something.