McDonnell Odometer Original Box Lightning Speed Indicator Tachometer

This is a nice, clean, antique tachometer, referred to in the instructions as "THE LIGHTNING SPEED INDICATOR, CUTMETER, AND LINEOMETER" as we guess the term "TACHOMETER" was not the common for a instrument designed to gauge revolutions per ft., this one for belt line speed gauging it appears by the instruction given inside the original box. The speed indicator itself is marked in fancy script "MCDONNELL ODOMETER CO. CHICAGO ILL." on the white dial face. The face measures 1.62" diameter, with a good glass crystal type lens, no cracks, a little internal oil on the inside of the lens, like tiny spots. This indicator does work smoothly, however we are not quite sure how to test it for accuracy, as we are not sure what size the original rubber tips were, as the instruction mention more than one, but do not say how many interchangeable tips came with it. The graduations are 10ths of a foot it says, and there is a inner dial that will go up to 10, (at 0 in the pictures), and the inner dial is numerical, and does work. Certainly a rare and collectible gauge with a very nice nickel plated metal body and lens shroud, nickel plating is about 95% intact. There is a good solid rubber tip on the end of the free spinning spindle, it is solid, and appears to be the tip that the other tips must have fit onto, as it will not come off. The original box is in very good shape, a folding cover type with good black paper covering, overall in very good shape with a nice inside label and instructions. A rare gage!