Doc,....I think you're right on the registration number. It was a 4" barrel, with sheard front sight. Had the rear u-notch sight, and the buyer had requested it to be dead-on at 20 yds.
Original purchaser was Michael Clevis, and there was a signed letter from his grandson that the gun had been in the family since it was purchased. It also had copies of the original work order sent to S&W, and their response back. Also had a letter of authenticity from the SWHF.
The copy of a photo shows Michael Clevis as the USSS agent working the left rear fender area of FDR's limo, while FDR and Eleanor are seated in it.
It is for sale......Price is $14,000.