Dan, 
I don’t think those Billings wrenches are at all rare, as they were popular in
the golden age of bicycling.  The likely production total is in the thousands.
I’ve seen several; never wanted one myself, but they have turned up.

There were likely competitors as soon as the patent expired.

The book you need is now out of print: “American Wrench Makers 1830-1930” by the
late Kenneth L. Cope.  I just looked at the price of used copies on Amazon and
I’m stunned!  Perhaps you can borrow it on inter library loan.

The Alloy Artifacts website may also yield useful information.

In my mind’s eye, I see a fellow on one of those early “Pennyfarthing” bicycles,
with the huge front wheel, carrying one of those in a pocket.

I agree with you that these wrenches are not worth $20.  Maybe that’s why I
don’t have one!

In the course of this thread, Michael Suwczinsky wrote something really
profound, something that rings true after about 45 years of tool collecting:
“I find that I only regret the tools I didn’t buy, when I had the chance.”

Oh, how true that is!!!  The same concept, in almost the same words, was
conveyed to me years ago by one of the world’s foremost tool collectors and
miniaturists!

A search of the archives will turn up some threads I’ve written about “the tools
that I’ve let slip through my fingers.”

John Ruth
Metuchen, NJ
Sent from my iPhone