I agree that using a 90 day window for collecting would make many things seem rare. My perspective is 40 years of searching about and you find one here and another there makes them not seem so scarce.
Well, although my focus on collecting Machinist Tools was admittedly subdued for the past two decades, I am certain that, judging by the items I sold you even 30 years ago, that I certainly paid my dues in searching them out.
You were a very early collector, and have travelled many miles and put in countless hours over the years.
And never discount the fact that, as you have often and honestly admitted, that demand for early Machinist Tools was very light in your early days.
These little guys are not easy to come by. I would never have passed one by without questioning what it was, at least.
So they seem scarce to rare to me.
I have just one, and will post pics tomorrow.
And, at least I have discovered Catalog No.19, circa 1910, has only the modern, screwed-on version of the No.12 Protractor Head level offered.
Starrett stubbornly clinged to the older concept for too long, but at last saw wisdom.