It's a rather interesting story. We've discussed it several times here in the Forum; a search on "Revell Eagle" should bring up a couple of threads. The outlines of the story, as I understand it, are as follows.
Back in the late fifties (or maybe it was the early sixties), the late Harold Underhill published a book called Sail Training and Cadet Ships. Like most of Underhill's other books, it was illustrated with a large number of well-drawn plans. One set, which ran over at least two pages, showed the class of barques built by the Germans in the 1930s. I can never keep all the names of those vessels (each has had several names) straight in my head, but I think there originally were six of them. Two were named Gorch Fock and Horst Wessel. After WWII they were turned over to the Allies as war reparations. The Gorch Fock went to the Soviet Union, and was renamed Tovarisch. The Horst Wessel went to the U.S. Coast Guard and was renamed Eagle.
Mr. Underhill was careful to note, in the text of his book, that, though the six ships in the class were quite similar in most respects, they differed significantly in length. I don't remember whether all six were of different lengths, but the Gorch Fock and Horst Wessel certainly were: the Horst Wessel was something in the neighborhood of 24 feet longer. The drawings in the Underhill book - as he explained quite clearly - depict the Gorch Fock.
Unfortunately, over the intervening decades those plans have been reproduced and sold many times, and somewhere along the line the fact that they actually just represent the Gorch Fock accurately has fallen by the wayside. So far as I know, almost every commercially-produced model kit purporting to represent the Eagle has been based on the Underhill plans. (The one exception was the 1/200 Imai kit, which apparently was available only briefly sometime in the 1980s.)
It should be emphasized that nobody, so far as I know, has been practicing deliberate deception here. Underhill was absolutely up front about the fact that the drawings were of the Gorch Fock - and so is the U.S. Coast Guard.
To confuse things further, back in the 1950s (or maybe it was the early sixties; I'm not sure) the West German government built a new sail training ship and named her Gorch Fock II. (The earlier one is sometimes described as Gorch Fock I. Heller, incidentally, produced a nice Gorch Fock II on, if I remember correctly, 1/150.)
The Revell Eagle, according to Dr. Graham's history of Revell, was originally released in 1958. It was based on the Underhill plans - which is to say that its hull was about 24 scale feet too short. Dr. Graham lists its scale as 1/254; on that scale the discrepancy works out to about 1 1/8". Whether that's important enough to matter is, of course, up to the individual modeler.
The Revell designers apparently were trying to represent the Eagle in her then-current (i.e., 1958) configuration. She'd changed quite a bit since the thirties: her original double-spanker mizzen rig had been changed to single spanker, her original figurehead (a big eagle, with the swastika in its claws replaced by a USCG seal) had succumbed to rot, and had been replaced by a much smaller eagle (affectionately known as The Duck) that had originally been on the bow of an earlier CG training ship, the Chase. And various modern fittings had been added, most conspicuously, perhaps, two big Coast Guard motor boats.
So the original Revell kit was a reasonably accurate reproduction of...well, nothing. It was sort of an Americanized, 1958 Gorch Fock.
I haven't seen the kit Revell Europe is currently selling as the Gorch Fock outside the box, but I've looked at the online instructions and the photos on the box. It looks to me like it's nothing more or less than the old Eagle kit in a different box.
The Revell kit probably could be turned into a nice model of the pre-war Gorch Fock I with some work. Such things as the boats would have to be "back-dated," the extra spanker gaff would have to be added, and the modeler would have to do some research regarding the anti-aircraft guns that (I think) she carried. (I know the Horst Wessel had a couple of them.) The modeler wanting an accurate Eagle (or Horst Wessel) will have to hunt up the old Imai 1/200 kit, or work from scratch.
That's the story as I understand it. Hope it helps a little.