Posted By:
Scot Reader
Recall that Kleinow (Boston) and Smith (Chicago and Boston) are not "true" 460-only subjects, but are really 350/460 regular print (RP) subjects in disguise. That is, these subjects experienced the 460 portion of the 350/460 RP print run, with their counterparts Kleinow (N.Y. Catching) and Smith (White Cap) having experienced the 350 portion of the 350/460 RP print run. That is why Kleinow (N.Y. Catching) and Smith (White Cap) are about 1.5X scarcer than a typical 350/460 RP subject and why Kleinow (Boston) and Smith (Both) are about 3X scarcer than a typical 350/460 RP subject. That is also why you don't see Kleinow (Boston) and Smith (Both) with backs that are characteristic of the 460-only series, such as Sovereign 460 and Sweet Caporal 460/30.
Now, the Polar Bear back was fairly prevalent in the 350/460 RP series, accounting for some 13.8% of all backs in that series. Meanwhile, all the variants of Piedmont 460 and Sweet Caporal 460 combined for about 24.4% of all backs in that series. So, if you assume that about 90% of the Polar Bears were printed during the 460 portion of the 350/460 RP print run (say 12.2% out of the 13.8%), you would expect some 1/3 of Kleinow (Boston) and Smith (Both) to have Polar Bear--which seems at least close to in line with reality. So my guess (and it is just a guess) is that Polar Bears were printed heavily late in the 350/460 RP print run, which accounts for the high percentage of Kleinow (Boston) and Smith (Both) with Polar Bear.
Of course, if this theory is true, you would also expect VERY FEW Kleinow (N.Y. Catching) and Smith (White Cap) examples with Polar Bear. Not sure if this is the case.