Hollywood's "it" couple for a hot minute in the '50s eloped in San Fran in January 1954 and took a plane to Japan shortly afterward to celebrate ... but there was also some baseball business to handle.

Their photo album from the trip features several shots of the couple, but there's also a running storyline of the MLB legend -- who was a few years retired at the time -- and his old baseball buddy, Lefty O'Doul, trying to get baseball up and running in Japan.

Looks like Lefty didn't mind being the third wheel either.

All in all, there are 30 honeymoon pics in the velvet-bound album, with each photo measuring 7x9 inches or larger. It hits the auction block on February 22 at Heritage Auctions with a bid of $5,520 to kick things off, but it's expected to fetch over $10k.