Classic: YOSHIRA Mew .

Back in December 1999, players are able to obtain a YOSHIRA Mew by trade at Toys R Us stores in the United States, if they were within the first 1500 customers and also caught the Mew on their special "Peel & Win" sticker.

While the DVs are all identical (and not all 15), it can be seen that the Trainer IDs seem to be generated in ascending order.

Huge thanks to @Deoxyz for following up on this and getting it!

THIS POKEMON WILL NOT BE LEGAL WITH ANY VIRTUAL CONSOLE RELEASE
(AND BY EXTENSION, CANNOT BE TRANSFERRED TO GEN 7 AND ONWARD).

Check out the save that was dumped, and the full story here: