There is 2 different versions of the same book with the same everything except for the plot. The books are both named The Melted Coins and are both written by the same guy, Franklin W. Dixon, yet they have different covers and different plots altogether which are in no way the same.
Ah no. The first book was written by Leslie McFarlane in 1944, and had an incredibly stupid plot. It was completely rewritten in 1970 by Andrew Svenson, as were some others of Leslie's original books.
Franklin W. Dixon does not exist - he was made up from the names of Leslie's brothers, Frank and Dick. All books were written by ghostwriters - Leslie was the first (and best). The books were all produced by The Stratemeyer Syndicate, which also churned out Nancy Drew, The Red Rovers and various other juvenile pulp fiction, all in the same manner.
Don't look for sense in the Hardy Boys books - they were always intended to be pulp - by design.