Okay, here's the Reader's Digest version of my conversation with Gary Quinlan.
Hubalek's heyday was the 20's and 30's right up to just before WWII. In 1906, at 17, he shot a world record score offhand. He was exclusively an offhand shooter and continued to set records.
He did make centerfire guns/barrels. He was a general gunsmith and did repairs and such in addition to making the best .22 match barrels at the time.
Gary has a catalog that is little more than a small pocket size pamphlet that lists .222 and a couple other varmint calibers which were big at the time. In the margin were a couple other calibers hand-written by someone and I think .22 Zipper was one.
He asked how the name appeared on the barrel. On mine is is A. HUBALEK. Gary said that of all the barrels he's seen over the years, the centerfires were marked A. HUBALEK like mine and the .22 match barrels, for which his is famous, were marked A. HUBALEK SPECIAL. So, although not documentation in the pure form, a pretty good indication that he made the barrel in .218 Bee and it is not a later rechamber. Also, the fact that the .218 came out in 1938 put it in his heyday period. Gary did say that he started making centerfires towards the end of the 30's as WWII approached.
His health deteriorated after WWII and he died in Nov of 1952, same year I was born.
I sent pics of the rifle to Gary because he said Hubalek's wood was distinctive, and he'll be able to identify if he built the rifle. I told him it had a thin Whiteline pad that was a bit crispy. He said they were around back then and he was known to use them.
If I get more info after Gary looks at the pics, I'll post it here.