I am working on a blog post about Title Blocks and doing some research on adding a Scale value to a Visio text block and came across an interesting post by the shape miester Visio Guy (AKA Chris) (my usual research method is to review blogs by the Visio MVPs)
Detect-drawing-units-in-the-shapesheet
In the comments, one of the other Visio Masters mentioned he used

To determine if the document was Metric. I thought that there must have been an easier way and remembered that Graham Wideman had mentioned a Metric cell in one of his books on the shapesheet.
Section 1, Row 20, Cell 2
So, with a little VBA I gave it a test.

So, by checking this cell, you can determine if a Visio document was created with US or Metric units.
So, if you are serious about working with the Visio shapesheet, get a hold of one of Graham Wideman’s book and follow Chris (Visio Guy), David (BVisual), John (VisualSignals), Scott and the other Visio MVPs.
John… Visio MVP in x-aisle
JohnVisioMVP.ca
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A good find, and this hidden cell has the name Metric, so can be referred to directly from other cells, eg TheDoc!Metric
I like your answer better. 😉