They're listed as being from 1953 in the CJ book. Unlike many of the "deep drawn" animals, no unmarked pieces are listed in the CJ book. These are always found marked "Cracker Jack" to my knowledge.
Additionally, they always have a secondary marking, also unlike any other "deep drawn" animal to my knowledge. They have either "E1", "E2", "E3", or "E4". I'm not sure what the significance of that marking is, unless it's the mold position on the runner.
If you have any polar bears for sale or trade, let me know.

