From the 1954 Bear Catalog.
"A sleek longer-limbed beauty, the Polar incorporates many of the Grizzly's graceful characteristics but without recurved ends. Exacting tournament shooters and discriminating bowhunters who prefer the straight bow find that Polar has been designed to meet their requirements with complete satisfaction.
Like all other Bear Bows, this model is faced and backed with fiberglas over a weight-saving hard maple core. Polar is a straight bow having shooting qualities usually found only in recurved bows, yet with all the inherent accuracy of the straight bow design.
It's new style, form-fitting, saddle-type leather handle includes the double arrow rest and near center shot features."
Length, 64". Draw limit, 30".
Weights, 35 to 75 lbs.
"Available in 68" length, 32" draw limit, at no extra charge. Both the 64" and 68" models are also available in heavier weights-76 to 100 lbs.-at $10.00 extra. Every Bear Bow is registered and Guaranteed. When ordering, specify length, draw length and weight."
Price $29.50
In 1955 the limb design was changed to Semi-recurve and still offered the double shelf. As near as I can tell Bear offered the double shelf through 1956. In 1957 the riser was re-designed and the double shelf wasn't offered again.
Hope this helps a little.