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.