AJS Stormer it is! Now I like the poster even more… Never heard of the AJS brand of motorcycles before this. Thanks
@Charles S and everyone else for the help!
Alas, many of us knew AJS as "Matchless" and when I thought I remembered that and googled it, I discovered that many of those British companies were bought up by Norton.
The vintage MX scene has made a real comeback, not only in the US, but to a larger extent, Great Britain. The MX bikes where there first, while in America we were stuck pushing leaky Harleys down the road, or removing the fenders from our Yamaha street bikes to make them "off road" machines.
You have a very old poster there, since that bike currently runs for between $7K to $10K, and no one is getting them dirty, much less racing them. Good score, and good search by Charles. I still like my Greeves answer though. I remember them too.