I know I've searched and I can't find out what it is, and the writing on the seatstay spoon is too oddly written to know for sure what letters they are. I would say it's definitely a very nice older custom made bicycle made by a custom builder who probably didn't build too many. He did however use Nervex lugs if that matters, Nervex were the best artistic lug available at the time and are regarded today as highly collectible.
The closest I could get to the name was Hoijfs written in a old vivaldi script, but that word makes no sense and nothing pops up on the internet with that name, therefore I'm going to have to presume it's either a foreign language and or a small custom builder perhaps French.