I just picked up two Stingrays at a local sporting goods establishment, and the rims are different. Has the mold been tweaked? One rim concaves in a little before the lip, and the other is smoother and thicker.
There are two different Stingray molds. Ontario and San Marino, as it says on the engraving. The difference you are describing however, sounds like a molding variation of the same mold. The mold has not been tweaked.