I have extracted it and compared with the 2.1 version.
Outside of the modified title it only shows two slight modifications:
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Edit: I arrive too late to this old known Rom.... it seems it is a 2.1 modified Rom, because PRINT VAR$
gives the 2.1 correct text....
On the other side, being it a useful relocatable extension, it seems for me an original Rom, not a hacked Rom.