Thread raised from the dead.
It has been a couple of years since I started this thread. Since then, a lot has transpired and I no longer think the Linto cover noting the event of FDR's death is necessarily "fake." I also now have strong reservations about Sherman's treatment of the Victory, VT covers in his catalog.
As for the FDR cover, a while back I acquired all of Dave Ahl's remaining inventory of Victory, VT covers (he offered them for a price I could not turn down) the bulk of which where Linto covers. There were enough for me to undertake some statistical analysis of the distribution of them over time based on the numbers that Linto placed on the back of each cover. Statistically, the number on the back of the FDR cover suggests that it is unlikely that it was prepared very long after FDR's death. A large number of the Linto covers appear to have been service by Harold Stark, as represented by the FDR cover. I surmise that Stark served as an intermediary for Linto with the Postmistress of Victory, VT at the time in producing the steady stream of Linto patriotic covers with Victory, VT cancellations. When a significant event occurred, Stark probably phoned the Postmistress (Elizabeth Lucy Stanley) requesting cancelled covers (probably both blank and covers already addressed to him as in the FDR cover depending on circumstances) and the cancelled covers without cachets were then sent to Linto in Portland, OR where Linto would produce cachets. The process of getting blank covers cancelled and applying the chachets later was quite common in the production of wartime philatelic event covers.
Sherman drew attention to the AM postmark on the FDR cover and how it was impossible to have known of FDR's before much latter that day. That doesn't mean much. In a large collection of Victory, VT patriotic covers, I've only ever seen a single one with a PM postmark. I suspect that Mrs. Stanley never bothered with changing the time of day on the cancellation device when generating patriotic covers. So it is possible that the cover was in fact cancelled on April 12, later in the day. It is also possible that she might have been contacted later in the day, but didn't actually cancel the covers until the next day.
Even if they were not cancelled for a day or two after the event (much longer than that becomes statistically improbable), how is that any different than the way FDC's are produced today? I don't know how strict regulations were back then about backdating, but the Victory, VT was processing a huge amount of patriotic covers during WW II and given that these were purely philatelic creations I doubt anybody lost any sleep if a cover was backdated a day or two after the event being memorialized on the cover.
Here's a press clipping of what the little PO in Victory, VT was up to in 1945:

What's the likelihood she could have serviced 2500+ covers on May 8? It could have been done, but I wouldn't be surprised if she took a couple of days producing the covers. I doubt if anyone ever gave it much thought at the time as to whether the cover was actually postmarked that day, or the day after.
Sherman bought into a theory propounded by Herman Herst that somebody got a hold of the Victory, VT cancellation devices after the war and produced a bunch of fraudulent covers. But Herst's speculations are hogwash, and do not stand up to close scrutiny. But that's a story for another day
Basil