For what it's worth, I don't think Bear made the "Alaskan" until 1959. The "1953" on the lower limb silkscreen refers to the patent date of the working recurve limb.
As to the cracks. Vertical cracks like that are common in the older Bears, both on the back and belly side. If you had a crack like that that went horizontal, it would be a different story. I've shot mine with vertical cracks like that for years and never had a problem. If you are really concerned about it, fill it with Loctite 420 (or similar super glue)and you shouldn't have a problem.