A7. 10x1 male spigot down with 15mm extender
Links to photos of examples:
This valve fits early 1987-93 Tomos top tanks with 10×1 internal threads. After 1993-94 Tomos top tanks have 12×1 external threads and take valve A17b.
The knob has to be removed in order to screw on because the tank wall is too close. Once installed the round knob goes through a one inch hole in the right plastic panel below the tank.
Here it is shown without the metal cup and rubber ring, but those things are included. The 15mm length extension includes the cup and rubber.