Need some help for a writer on old vs. new stamp values
I have a writer friend who is creating a time travel story where the hero goes back from 2020 to 1965. The hero needs to bring with him in then time machine some reasonably liquid asset he can use in 1965 to generate some cash, an asset he can get in 2020 that would be of greater value (inflation thrown in) in 1965 . Using current US cash won't work and most precious metals and diamonds, etc. are more costly now than they were in 1965. So, my writer-friend (knowing that I have a stamp collection) asked me for some help.
I suggested to him that his hero could buy some high end mint stamps in 2020 and get more value for them in 1965. My sense is that the stamp market is much less lively now than it was in 1965, hence there are stamps our hero could get today that would be saleable (to a stamp store, for example) in 1965 for a sizeable sum.
A strange topic, to be sure, but I wonder if the forum members could identify a group of stamps that would be worth $5,000 in 1965 (say, at 60% of catalogue) that might cost $2,500 today, in 2020? I could have answered this question myself a few years ago, as I had some old Scott's catalogues from that era, but I have since sold them off, and libraries don't carry them from 55 years ago.
Can anyone help here?