Here is the drawing which should have been present in the original documentation, and, failing that, should have been uploaded by ST's forum employees.
Note that the board outer tolerance is given as +0/-0.5, taking into account a previous statement that it's categorically 24.5mm, but then later on a pseudo-correction that it could be 25+-0.5. I'm doing my best to merge those two somewhat contradictory statements.
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A general plea to ST: please don't make your clients do this work for you. This is a somewhat pricey board, it should come with the support required to mount it. It should not take knowledge of how ST does other square boards, nor software for opening gerbers and drill files.
