There was a change in the materials used in the Commander in mid 1999. The scales and the liners were thinned a tad. The blade grind was changed slightly to retain blade thickness more towards to point. This is the transition from the First Generation to the Second.
In late 2000, the blade grind was changed back to the original design.
The "Mil-Spec" Commanders was a small run done with First Generation materials. These had Green-Tblades and were logoed with "Mil-Spec". Due to the low number of knives produced in this configuration, it's quit collectable.
EKI has since released a Green-T version of the Commander, in a Second Generation body and it does not have the "Mil-Spec" markings.
As with most of my posts this last month, this one isn't made from home, so I don't have the specs to give you. I'll see about updating it later.
hth
John