I recently won this Mexico 2-Reales 1756 M (Pillar/Columnaria). It was listed as XF-AU at a local on-line auction. Weight is a bit low at 6.29gms. I deduced that while details are sharp, 'harsh' cleaning and pitting can be observed. So this might be a sea-salvage coin, which can possibly explain it's weight.

This is actually my 2nd Mo 1756-M, weight=6.53 gms (left), so I was able to compare it with the new one (right). The new one also has a bit larger flan.

Looking for your opinions.