Older model threaded headset

[river16]

Hello, I have what seems to be an older-type threaded headset on one of the bikes that I am working on. Instead of the hex-shaped nuts, I have a completely circular one that has two notches in it where it seems like the removal tool would fit. Problem is, I cannot find what type of threaded headset it is or what type of tool is used to remove it. Does anyone here know how to work with one of these?

Any help would be much appreciated.
Thanks,
~Derek

[cyclerUK]

The notches are usually for a "C" spanner.
But I have used various methods for slackening etc.
I don't see why you couldn't use the now standard hexagon style ones.

raleigh and others also supplied a multitool which usually included a "C" spanner as part of it.