This is a similar mark on this CD 165.1 Whitall Tatum. This is a larger arc. The explanation is the same:

During the molding process, when the glass flowing into the mold was snipped off, the end of that piece of glass could cool a little before the new mold in the semi/automated press spun into place. With it slightly cool, and the top of the dome (which is the bottom of the mold) also being slightly cool, that tip of the molten glass would not get fully pressed flat in the mold, and would leave this crease.