Year Code Letters

The answer to your question is generally no.

The first Dominator engines had the Year Letter, Model Number and Engine Number all stamped on the left hand side of the crankcase. Just below the barrel.

Around 1956 this changed witth a fancy Norton Badge taking over the previous patch. The Year Letter and Model Number stayed near this badge but the engine number migrated to the front, top left of the crankcase just beneath the 5/16" barrel stud/nut.

Here it remained in solitary confinement until the arrival of the proper 500SS and 650SS engines in the UK in late 1961. Then model numbers appeared as pre-fixes to the engine number. But not on every crankcase until the production moved to Plumstead. Don't ask me why???

Attachment show my previous 99 engine lower half displaying its numbers and letter.