Glad to report that BP 0543 is amongst you after spending 30 years in bits in very old boxes. I have been an avid reader of the forum which I have found to be both interesting and helpful.
For some of us on the other side of the pond, your registration refrences are rarely understood. I have attended New England MGT Register seminars on English Car Registration, but I either can not retain it or really never understood it. In any event giving the model and chassis number when refering to a car back on the road would at least have more meaning to me. Sorry if I am in a distinct minority.
Yes you are right, should have been PB 0543 (the chassis number) Registration and engine numbers tend to change over the years, but chassis number live forever!