Giants Postcards from 1976 or 1977

Ryan surprised me by including a bunch of postcards featuring Giants players in the package he sent me last week.  They appear to be from the mid-1970's:

Shozo Doi

Isao Harimoto

Tsuneo Horiuchi

Shigeo Nagashima

Hisao Niura

Toshimitsu Suetsugo

Assuming they're all from the same set or issued at the same time they can be from no earlier than 1976 (since Harimoto didn't join the Giants until then) and no later than 1977 (Suetsugo's final season).  Since Suetsugo only played in 3 game in 1977 the postcards are most likely from 1977 1976.

Here's what the back of Harimoto's postcard looks like:

I don't know what the text on the bottom left says but I do recognize Harimoto's name in it.  The text is different on each card.