Identification help

I picked up a couple Norton’s a couple weeks ago. I’m hoping you can help me identify one of them. The owner said it was a 500 and that’s all he could tell me. It resemble my 1964 Atlas.


Serial number is 20/ 117** p

thank you

20 is code for Atlas 750.
p is code for Plumstead
117 puts it in the year 1966

Great!!! Thank you.