The H is the Hocking mark that is usually on the back side of globes at the top, but sometime on the front side. The 2, 3, & 15 is the mold number used to make the globe. Hocking also made globe types other than for the Comet. Hocking was one of 13 confirmed lantern globe manufacturers, but there were probably others. Most, if not all of the H marked globes from molds 1 through 20 were Dietz marked globes, while molds 21 and up were unmarked globes. I cannot confirm it, but I believe the globes with the numbers before the H were made earlier than the ones with numbers after the H. I know of no Hocking globes with manufacturers markings other than Dietz, but Dietz used several globe manufacturers.
John M