Cubs historical sleuthing: Early Ron Santo edition

Al Yellon created Bleed Cubbie Blue and has been its managing editor since 2005. He's also written three books about the Cubs, the latest is "Chicago Cubs Firsts."

Here is what we know about this photo at first glance:

Ron Santo is batting at Wrigley Field

The Cubs are playing the Mets (logo on the catcher’s sleeve)

The Mets pitcher has a number that begins with 3

It’s cloudy (no shadows)

There’s very likely a pretty small crowd (only one fan visible, lots of empty seats)

So, this could be just about any time in Santo’s career, right?

Well, no. In fact, we can pinpoint this to one specific at-bat. This was one of my favorite sleuths ever, given the apparent lack of information at first glance. But…