So, back to HBs.
From what I can tell, continuing on what I posted earlier and then reading/researching more -
HB pattern itself has been around awhile, modified from a Biscayan style trade axe. This is discussed by D Cook, T. Lammond, and H. Kauffman. When that actual modification really happened, I don't know. Basically the addition of a poll to the axe and the bit being widened. D Cook states that the new "american" axe, (one with a poll, not necessarily HB) was known by the mid 1700s. T. Lammond states that changes in the American Axe weren't seen until the early 1800s, when America could make its own steel, and the prices dropped and gave more freedom for blacksmiths to try and evolve different patterns. I would assume that this means the first axes with polls made in North America, started in early 1700, but were limited due to resources, and then with the end of the 1700s and start of 1800s as the resources were there the American Axe took off. This makes sense as this correlates with the start of the axe companies as we are familiar with - Mann Edge(original Manns), Collins(1826), etc. i bet the true evolution of the HB pattern follows this latter timeline of late 1800s. T Lammond also states that the purpose of the HB was to provide a tool that could be used for a variety of applications not readily possible with a hatchet, while at the same time reducing the weight of the axe so it could be carried along with other hunting and camping gear. This makes sense, and has been discussed before. When this actually happened I cannot find a time reference to however.
Popularity. One has to remember that at around this time, for every 10 Americans there was 1 Canadian. This technically isn't too far off from today, but obviously the concentration is different, and was tremendously different back then as well. I would stir up a notion that the original HB pattern could of been around in Canada for years before it being seen in any kind of amount in the lower 48, or even by one of the axe manufacturers.
Standard - In the hey day of axe making, in the golden years as it is sometimes called, there were who knows how many axe head patterns. 300 is probably some reasonable number. In 1921 axe heads were standardized into patterns for the sake of simplicity. Some would be added, some would fall off and no longer be manufactured due to want/demand. Question - where was the HB pattern? Surely it was out there seeing it evolved from the trade axe which originated a couple hundred years prior. This leads me to believe it was out there but in limited number, and probably still well north of the lower 48. Heck the Rafting and even the Cedar axe were on there but no HB.
Back to area/popularity - So, if we put this all together, plus the fact any major axe makers really didn't get going in Canada until around 1900, I would bet the HB pattern was technically around, but didn't get any recognition until Mann Edge and Kelly were in the area.
References - The earliest I have in my catalogs for a HB to appear is in Collins 1936. There are patterns similar to it listed in earlier catalogs, but not called HB. This again, with what has been listed, makes sense.
Vintage specimens - I have never seen a really old HB axe. I have and have seen pre 1900 and pre 1800 axes. I have never seen this for a HB though. Doesn't mean it isn't out there, but I have never seen one.
This leads me all to believe that the HB pattern(as we see it today - narrow eye, big wide bit, long from poll to bit) was probably rediscovered in the early 1900s, say 1920s by one of the big companies, Say Collins, and they went into production to feed the nitch for that axe, which was the traveling/camping/backpacking person that needed a light weight axe with more uses that a hatchet. It makes sense overall, explains why you don't really see it prior to the early 1900s, its nitch, and then popularity. The only other explanation is that it technically didnt really exist prior to say 1920s and one of the major axe makers created it and made it, and then the others copied it, which was prevalent at the time(undercutter, cedar, rafting, on and on). I don't think this is the case as the big companies were copiers not creators(see Cedar pattern). The fact that I can't find a date for it leads me to believe this.
Thats it. My mind is spinning about this axe. Axe history is interesting indeed. Ugh!