I just did a quick look through "The Encyclopedia Of Matchbox Toys" by Charlie Mack and did not see it in the book. This book is from 1997 though and it may have been done after that or I may have missed it...
Yes I did wonder. The tag says code 6 so what does that mean? Could just be a promo for the museum and not a personal piece for him. I just wouldn't want to overpay since the casting itself is quite common anyway.
Code 6 means personal label. There are actually 7 Codes referred to in the Londonder book. You might ask if the seller has the book to offer as I do not know where else they would get these coded. It is a pretty good reference.
That solves that then. Good to know. From the description one might easily assume that this was presented to Charlie at some point or that it could be any other semi-official Matchbox release. Instead, the owner took a bus and stuck home made labels on it. Not really worth my money then, thanks.