That's quite the oddball: I'd say "custom" but by who? Dunno...the fork could well be from another era and not original to the frame, but never saw that crown before, very distinctive SLIGHTly like a '90s Cinelli crown but...not.
As for what's there: the RGF (Gargette Bros) shell is FR but widely used by many Brit builders, those track ends look "early" and somebody might reco the make but the stays appear to be fillet-brazed (or bronze-welded in BrEn usage) to them which is another detail more common to British practices.
What's the threading and seatpost size?