Gearbox numbers starting with SB

Hi everyone, although i have been visiting this site for a while, and have already sourced some great info, however this is my first post. I own two Norton's, a 1960, model 88 Dominator, which is on the road and ridden with great pleasure regularly, and a non matching numbers commando that i am currently starting a custom build on. My question is about the commando gearbox, it has some strange markings that i haven't seen before. Usually i would expect to see a number starting with either N or NA followed by the number, my box has the following markings, SB 040122 i have spent some time researching these numbers on the net and can't come up with anything. Any help from other members would be greatly appreciated. Great site and thanks for your help.

Welcome.

B73 said:

Usually i would expect to see a number starting with either N or NA followed by the number, my box has the following markings, SB 040122 i have spent some time researching these numbers on the net and can't come up with anything.

Click to expand...

"040122" is the 'casting' or 'foundry' number and as such it's found on the majority of Commando gearbox castings so it's basically irrelevant because it isn't the actual part number of the component.
'SB' would appear to be (part of?) the foundry logo.

B73 said:

Usually i would expect to see a number starting with either N or NA followed by the number,

Click to expand...

Commando boxes are just stamped with a 6 digit number on the top mount of the box,
and its the same as the engine number (ex-factory).
You can just see it on the top of Les's pics above.

Its been discussed here before that sometimes there is also a stray stamped letter,
the meanings of which appear to have been lost in time - could be a batch number maybe,
or some sort of factory work or rework mark ??

Thanks i will have a better look, used to the Domie where it is located on the kick start side on the case.

It is a foundry mark and die code, it would help identify the die in the event of an issue, wear, castings issues etc. In the days of old there were most probably over a dozen dies in use or replaced just for this one part maybe from different foundry's - they don't last forever.

Condition of the shell and the quality of the casting are what counts in determining whether it is good to use.