John, I think you nailed it on the SqSqDia mold (as abbreviated in some of the chip guide books).

However, I think the "Ex Heavy" on the order card probably refers to the chip weight (in grams). See the H.C. Edward page on ChipGuide here:

http://chipguide.themogh.org/cg_chip2.php?id=NYNYHC&v=1984939660

The black chip "EX.HY" illustrates an extra-heavy version on the HCE mold.