Right. Tomity says 20% of Keirin racers still go for 110 spacing. Some makers like to still use this spec.
I have some 110 njs hubs if anyone needs some.
If it has no stamp it is not a njs keirin frame. Like someone said it has nothing to do with the quality, most likely, just the frame was not made for Keirin in Japan, so was not stamped. It might be exactly the same in every other way to a Keirin frame of course.