Mk 2 steering lock

My top yoke is a Mk2, the steering lock hole is 19.9mm dia counterbored 22.6 mm x 8.3mm deep at the top.

I bought a supposed Norton Mk2 steering lock, the body is 18.5mm , 18.2mm at the bottom with a 20.1mm dia rim, It looks like the lock should be retained bi a thin pin tangentially through the bottom of the hole. I could throw it into the hole in the yoke from the other side of the kitchen.
Is the lock just sh1t or has my yoke been modded at some point.

Sounds like you could have bought a Mk3 lock if it has a hole for a pin.

The Mk3 lock also fits from the underside of the yoke so it has no lip around the top edge.

No it isn't the mk3 Neinman type lock, it is the Mk2 FS key type

The lock does not have a pin hole, the housing has the hole right at the bottom on the LHS

IMHO, the steering lock on a pre-MK3 Norton is a joke. Nothing holds them in and you can just push them out from the bottom. The same lock on a Triumph is very hard to get out as it has a special screw to lock it in place and then you fill the screw hole with lead or whatever after the screw is in and then paint over it.

Not sure about the MK2A but AFAIK, all the pre-MK3 850s use an "ANG" type yoke and they are the same and use the same lock as the 750s with the stem attached to the top yoke.

In other words, I generally don't bother to install them.

According to the Mk2/2A supplement some Mk2/2A possibly had a yoke with a Neimann lock, however I don't know if this ever happened or if it was cancelled until Mk3.