Need Help With Code

I am having problems with a couple of the letters on my 56 Sunliner. What does "BG" stand for? It is the 6th & 7th digit?
and what does the letter "P" stand for? It is the last digit.

Thanks for any help!!!!
Jeff

Thanks DennyW for the reply. I was hoping this was a good site for help.Thank you very much.

JRicks