Hello, and welcome. nice item.
The Schooner Sir Winston Churchill was built in 1966 by the STA. wiki
The STA still exists as the Tall Ships Youth Trust. wiki
You could contact the Tall Ships Youth Trust and ask if any records exist of how these were given out.
I would guess everyone who completed a training cruise got one. The Wiki says there were 39 trainees per tour, and it appears to have operated until about 2000. 34 years times 39 medals, assuming they never changed them, makes 1326. They may have given some to funds donors as well, so the number is likely higher than that.
the Malcolm Miller is the sister ship of the Sir Winston.
The Numista catalog has an entry for the corresponding medal.
N#180848
Would be good if you could add yours to the catalog.
You can duplicate the page for the Malcolm Miller coin, and just change the text and pictures.
your pictures are quite good, just need to remove background.
Jamais l'or n'a perdu la plus petite occasion de se montrer stupide. -Balzac