Throughout the 60's and early 70's the original 38 HB books were revised. #37 The Ghost at Skeleton Rock was originally published in 1957 and the rewrite was done only 9 years later in 1966.
the rewrites for #33, #34, #35, #36 and #38 were done in the early 70's, near the end of the revision process, but "Ghost" was done in the mid 60's.
Was there a reason why the rewrite was done so soon after the original?
Originally "Ghost At Skeleton Rock" featured the bad Guy's base in Cuba. Suffice it to say that when Fidel Castro came to power, even fictional characters could not travel to Cuba.
Fidel Castro came to power in 1959, so that makes a lot of sense. And after the Cuban Missile Crisis in 1962, I can see all the more why they would want to avoid having the Hardy Boys in Cuba at that time. (And funnily enough, it seems that now relations with the USA and Cuba are improving, as it's become at least more possible for US citizens to visit Cuba- something that was not allowed for quite a long while.)
(And by the way, The Ghost at Skeleton Rock is one of my favorites in The Hardy Boys series.) :) 8)
The Ghost At Skeleton Rock is one of my favorites as well. 007 James Bond goes to Cuba twice.