Yes, I know that I'm probably a total philistine, but somebody really needs to explain to me why you would ever need to make the fine adjustments that this stick is manufactured to allow.
Here we have the Micrometer Stick, manufactured by H.B. Rouse and Co. of Chicago (sorry that the pictures aren't clear). The Micrometer Stick was designed to supercede the Quarter-Point Stick, that was too fragile. The Micrometer Stick uses a body that is identical to that of the standard Rouse Job Stick, with the row of little rectangular holes along the rail into which teeth on the knee engage. The clamp is pretty much the same - the knee is what is different.
The knee, cast from pot-metal and consequently a little brittle, has a similar bar with two teeth that engage with the holes along the rail of the body. If you remember on the Job Stick, when you lift the clamp there is a little lever that, when turned 180 degrees, moves the bar with the teeth 6 points, thereby allowing the measure to be adjusted by agates as well as by full picas. The Job Stick has four teeth, while the Micrometer Stick uses a mechanism that has only two teeth. But instead of the lever as is on the Job Stick, the Micrometer Stick has a...well...a micrometer for adjusting the teeth.
The way it works is, you lift the clamp and then turn the little wheel on the knee which moves the two teeth by half-point intervals. The teeth appear to be able to move a full pica, so there appears to be a total of 24 possible adjustment points. I could be wrong on that, and it may actually allow more intervals than that.
But let me ask all you compositors out there: when is the last time that you needed to adjust the measure on your stick with this level of precision? Really! Is this necessary? It seems to me that this is the kind of technology that appeals to gearheads and equipment geeks, but has little practical value.
Anyway, this stick was apparently pretty popular, and I have several of them. This particular one is a stainless steel stick 9-3/4 inches long and 12 picas deep, with a capacity of 46 picas in line length. The stick is stamped with a number which is supposed to be matched with a number on the knee, but I don't find a number on the knee, so maybe Rouse just routinely stamped these numbers without matching them to a knee.
Postscript Feb. 10: Henry Morris tells me that one of the uses for the Micrometer Stick is when text has been machine set using the Monotype typecasting system, and you want to adjust the setting by hand. He says that the measure is often inexact, so you may have to adjust the measure in the stick by a very small increment to accommodate the line-length of the machine-set type when you begin making adjustments to the text. So that's one rationale for the need for this type of stick.