Vladimir, Roi Humbert is accessible from the USDA GRIN database -
https://npgsweb.ars-grin.gov/gringlo...ail?id=1133536
It looks like it got into the collection i 1938.
This is the listing for King Humbert (which Carolyn and I both grew from USDA seed years ago))
https://npgsweb.ars-grin.gov/gringlo...ail?id=1094691
That picture is pretty accurate of what I got from the seed.