I decided, and it should have been obvious all along....
Original Inflight G-BNLR BA Rendezvous World Tail. Not only was it one of my 1st BA 747s, it has stood the test of time (seen here with the later G-BYGC version) with its fabulous wing droop.
2x BRitish Airways 747-400 Rendezvous World Tails by
John A, on Flickr
It has also proven to be a selfless participant in my collection, serving as the donor model for no less than twenty one other “as flown” world tail custom 747 models, and two that never flew, but should have. I still have the original, and one spare, making a total of twenty five examples... By sheer quantity it must be a favorite.