Nice collections, indeed. I've always liked the Mr. Zip character. In fact, there's a local post office that still has a "life size (4' or so) wooden and fully painted Mr. Zip statue in their lobby, with their post office ZIP Code on it! (I haven't seen those in years.)
I also find it interesting that the USPS used the Mr. Zip logo in marginal markings for years, but never put his image on a stamp ... even the ZIP Code stamp from the 1970's would have been appropriate, but no, they left him on the margin only.
I think I asked this question before without a firm reply, but what was the last US stamp issue that had the Mr. Zip character in the margin? I think it ended somewhere in the mid-1970's, but not exactly sure when. According to the web, Mr. Zip was retired in the 1980's when the Zip+4 Codes came out.
Here's a classic advertisement for it that brings back memories!
http://www.youtube.com/watch?v=USUYRqiHq0I