Hey Charles, here's a little more info if it helps. I measured the rear dropouts and they are 5/16" thick...not sure if they're stamped or plate, but they appear to be plate. There are no holes in the headtube. There are no grease fittings on the frame and the light boss is on the right side of the fork.

After Jacksbike and Realestvin7 said they thought it was a Raleigh, I did more research and found this website that has Raleigh serial numbers. Here's the web address.....
http://www.jaysmarine.com/TH_raleigh_serials.html
According to this website, the serial numbers would match a Nottingham built bike in June of 1980. Does this sound accurate or do you think it might be something else with the new info?

Thanks again!