Here's a mini-mystery up on eBay (
Denny McLain Signed 8x10 Photo Auto Autograph White Sox Tigers 1968 MVP CY Young | eBay)
Images of Chicagoan Denny McLain in the uniform of the White Sox are hardly scarce. Topps, McCarthy, and others got him in Spring Training 1963 before Chicago had to choose keeping one of two first-year pitchers (Dave DeBusschere) and trying to sneak the other into the minors via waivers (McLain). Oops.
But this is a shot of McLain at Comiskey Park, almost certainly a Brace image. And whereas McLain might have "gone north" with the White Sox before they lost him to the Tigers, a) what we can see of the outside foliage looks like summer, not spring), b) while the White Sox didn't open until April 9, the MLB openers were April 8, but c) the White Sox opened on the road, not at Comiskey.
The likeliest guess is that McLain worked out with the Sox shortly after graduating from Mt. Carmel High in Chicago and signing with them in June, 1962. The uniform number (29) would've been unassigned then rather than, say, for a post-season unofficial workout in September, 1962, when it was worn by another rookie pitcher, Frank Kreutzer.