Thanx @gster. That's a cool approach. I'll try that tonight. I never did find the vertices I was looking for.

If I knew more, I bet I could loop through all the vertexes with MEL and compare their offsets from each other.

I tried cleanup with a cube, in which I snapped a couple vertexes together. I couldn't get it to identify the pair using different combinations of Cleanup options. The pair did show up in the hud as 2.