[nat]

I don't know what set the first Oh card is from, but that's definitely Oh. It looks to me like a later issue; I'd guess 1970s.

The other three cards are from JCM58, which was issued between 1975 and 1976. The first guy is Oh. The second guy is Sumio Hirota. He played 1972 to 1987, mostly for the Lotte Orions. Early in his career he had a couple good seasons, but was mostly a below average hitter. He stole lots of bases though; I'm guessing a good-glove no-hit center fielder. Think of someone like Rajai Davis. The last player is Jinten Haku, also known as In-Cheon Paek. He was a productive hitter: about 15 HRs per year, around the same number of steals. He was named to one best-nine. After retiring from Japanese baseball he went to Korea, and is still the only player to have posted a .400 batting average in the KBO.

As for type of card: these are still menkos. Traditionally menko cards were printed on thick stock, since they were meant to be flipped around and thrown on the ground. That's why these cards are so thick. Some sets are very robust - put a Goudey to shame.

On the other hand, I've noticed that menkos printed immediately post-war are often very thin. Much too thin to actually play menko with. My guess is that a shortage of paper had something to do with that. "Tobacco" menkos from the late 50s and early 60s are better about stock quality, but still pretty thin if you're thinking about using them as game pieces. Presumably paper supply wasn't a problem by that point. Maybe kids were appreciating the cards more as baseball cards than as menko cards in that period, and produces responded by cutting corners? If anyone else knows why the tobacco menkos are relatively thin I'd love to hear about it.