Ooops. Missed this Original Scott catalog cuts were made available for sale to collectors when Scott transfered their printing process from letterpress to a large offset web-fed process. This stamp comes with it's original box, but unfortunately does not have a certificate.
Somewhere I have a few of these as well. There was a time when a local dealer had a box full of these discarded from the printer of the Scott U.S. Specialized. I agree with John Becker that these are not $50 items.
Also, the listing is suffering from an all too common malady: apostropheitis, as in putting apostrophes where they don't belong. None is needed in the word cuttings unless you mean a contraction of "cutting is" as in "The cutting's coming up for auction soon."
"Cutting's" is actually correct here, being the possessive of the name "Cutting". Look at the photos of the catalogue cut in the listing, and you will see that the stamp depicted bears the inscription "CUTTING'S DESPATCH POST".