I'm hoping someone can either point me in the right direction for this research or has the information they can share with me.
As you may know from the thread I've been working on for the past two months, the 1934 National Parks series, which was issued to the public in perforate, gummed form only was also one of the sources of material which ultimately resulted in the need to issue the Farley Reissues, affectionately named Farley's Follies, in 1935.
Two sets of imperforate sheets of the National Parks stamps were presented by PMG Farley to President Roosevelt. These sheets remained in his collection until it was sold by H.R. Harmer in 1946. The sheets sold as a single lot.
The next time these sheets come to light should be sometime in the 1950's. I remember reading somewhere, before I became serious about this series, that Stanley Gibbons had purchased the sheets. Unable to find a buyer for the entire sheets, they decided to break the sheets up. In the process, they rubber stamped the back of each stamp with a half-moon logo for Stanley Gibbons and pencil notated "FDR" and the plate position of each stamp.
What I am looking for is an article, any advertising or other proof this occurred. I know that it did and every major auction house I've asked about it also knows it happened, but so far, no one has been able to provided any documentation.
If anyone has an ad (probably from one of the weekly publications such as Mekeels, Weekly Stamp Gossip, Linn's Stamp News or a like publication, please let me know. If you can upload a scan of it, that would be even better.
I look forward to hearing from you all! Here's one of the stamps from the FDR sheets for reference.

