Interesting 1959 Yomiuri Giants Game Photo - Korakuen Stadium
 

Dated Oct. 28, 1959 and the slug suggests that it is a regular league game.

Central League, I assume? Anyone have access to a 1959 schedule, to see if this was a clinching game etc?

The Giants were the Central League champion every year from 1955 to 1959, winning the Japan Series championship in 1955, but losing four consecutive Japan Series thereafter.

World career home run record holder Sadaharu Oh starred for the Giants from 1959 to 1980, and fellow Hall of Famer Shigeo Nagashima played for the team from 1958 to 1974. The Giants lineup, consisting of Oh batting third and Nagashima batting fourth, was nicknamed the ON Hou, ("Oh-Nagashima Cannon") as the two players emerged as the best hitters in the league.

If the date on the back is accurate then it is from the 1959 Japan Series. The Nankai Hawks swept the Yomiuri Giants in four games.
October 27th and 29th were played at Korakuen Stadium in Tokyo. The 28th was rained out.
Both Sadaharu Oh and Shigeo Nagashima were in the lineup on the 27th. Nagashima played, but Oh didn't on the 29th.

Since the front says it was a regular season game I guess it's possible that the date stamp was placed there later.

Thanks Robert!