Thanks for the comments, Chris & Mark.
Most of these PCL caps are Wilson, and yes, they certainly don't surface very often
Fredy, Jerry Cohen at EFF has indeed seen, and in most cases, borrowed these hats to model his replicas. We are both in Seattle, and are good pals.
Here are a few more: 1955 Oakland Oaks, 1958 Portland Beavers, 1960 SLC Bees, 1970 Phoenix Giants. All Wilson caps, all gamers.