Markerinbound - at a minimum - caught a vocabulary mistake on my part.
In Europe a glider license and a power license are two independent documents, where here we would simply have a Private Pilot Certificate with ASEL and glider ratings.
I should not have said
certificate. Kontrollturm needs to add a glider
rating to his certificate.
I just spoke to the local FSDO. The answer I got was that an "on the basis of" glider rating could be added to his existing certificate, but it would likely be easier, faster, maybe even cheaper to simply fly with a DPE/Inspector and have a genuine FAA rating.
Kind of sad we're doing all this talking and the OP isn't her to see/follow.