Unusual "printer's proof" fountain pen advertisement

We've all seen vintage fountain pen advertisements, either at pen shows, at a local meet up, or of course on ebay. This Sheaffer Sentinel ad is a little different though, so we thought we'd share it.

This is a "printer's proof", provided to the customer (the ad agency) to approve before running in newspapers and magazines. Judging by how narrow and tall it is, it was probably a half-page-width vertical ad. Look closely at the top and you'll see a list of the 24 major newspapers it was scheduled to appear in on Sunday, April 10, 1949.  We've included a close up of that section below.

This and several other "printer's proof" examples can be seen at our next meeting on July 11th. Hope to see you there.