Need help to ID motorcycle transmission

[N2BUICK]

Looking for someone or a site I could check to help Id this motorcycle transmission. Thought, maybe some of you guys have experience or a lead.
I think its 1960's, maybe British?
Thanks

 

[salvageV6]

I agree, looks 60's British Matchless, Norton?

 

[V6sleeper]

Maybe BSA

 

[N2BUICK]

Thanks for the info.
I was getting some hits on a, Norton connection also.
It seems, maybe there was a vendor supplying the transmission units to several motorcycle manufacturers?
This gums up the works, it seems,to tie the transmission to a manufacturer.
In 1967 I had a BSA, 500 Cyclone.
I wasn't paying attention to the transmission, for sure.