Additional 1852-O dimes have appeared with a Large O mintmark that has a thick oval. At first, it was suspected that a third reverse die may exist for 1852 New Orleans coinage. But a mintmark position comparison between two 1852-O dimes with thicker mintmarks and the Reverse 2 mintmark, from the plate coin, revealed all mintmarks to have the same horizontal and vertical positions between DIME and the bow knot loops. See below:

I believe that all three 1852-O dimes pictured here were struck with the Reverse B die. What remains unexplained is the varying amount of thickness in the mintmark ovals and the resulting variations in the opening in the center of the Large O mintmark.

When this reverse die is reused in 1853 for additional coinage, the mintmark size and shape matches that of the plate coin. I would appreciate any comments from Seated Dime specialist who may have a theory or explanation for this mintmark size situation.

 Plate Coin: G. Fortin Collection, NGC MS62