yeah i got the 250 ones, they are nippon seiki i reckon and the 185 are nippon denso. The 250 have the wider stud mounts and that is what all those replicas you see are for.
i bought a nos tacho thinking it would be right but its a nippon seiki and has redline from 8-9000 so i think it could be for a DR400 or 500? i will swap it for a TS185 tacho.