>There's some information in the header. Not sure how precise it is, though, as it's a single byte and I'm not sure it changed since VFP3. I remember it was documented somewhere (I read it in printed form with 2.6 manuals), but I couldn't find it in home()\tools\filespec.

It's in the help under 'Table File Structure' and/or SYS(2029).
VFP tables have value between 0x30 and 0x32 in the first byte.