Hamilton Watch Co. Map Measure (Opisometer)

I just received my recent edition of the Watch & Clock Bulletin (Journal of the National Association of Watch & Clock Collectors), and a small article with a photo, in the back of the magazine caught my attention. It reads:
"Remembering Hamilton by Robert L. Hostetter
The Map Measure
As I continue documenting Hamilton Watch Co. drawings in the NAWCC archives, I re-discover products like the Map Measure shown in the photo to the right.
I don't know how many were made for use by military personnel during World War II. But I remember that I had one of these gadgets in my collection as I worked on 11" x 17" drawings of parts used in watches and other things manufactured at Hamilton.
How this instrument came to be manufactured at Hamilton is unknown to me, but I'm sure that experience with making gears probably made it easy.
The back of this model is stamped:
HAMILTON WATCH CO. USA
And I have learned through research that it is an early Model 331."

After seeing the photo and reading the article, I remembered I had a couple of styles of this instrument. After locating them, I discovered one was made by the Hamilton Watch Co.

Shown above is the one I have (and it is exactly like the one pictured in the article), and the back is marked:
MODEL 33
HAMILTON WATCH CO.
U.S.A.

Wikipedia definition of an opisometer:

An opisometer, also called a curvimeter, meilograph, or map measurer, is an instrument for measuring the lengths of arbitrary curved lines.
An opisometer
A simple opisometer consists of a toothed wheel of known circumference on a handle. The wheel is placed in contact with the curved line to be measured and run along its length. By counting the number of teeth passing a mark on the handle while this is done, the length of the line can be ascertained:
line length = wheel circumference × teeth counted/teeth on wheel.
In more sophisticated models, sometimes called a chartometer, the wheel is connected via gearing to a rotary dial from which the line length can be directly read.[1]
The instrument is most commonly used to measure the lengths of roads, rivers and other line features on maps. Opisometers designed for this purpose provide scales reading the measured distance in kilometers and miles.
Early versions of this instrument were patented in 1873 by the English engineer Edward Russell Morris.[2] The instruments he produced were initially described as a Patent Chartometer although later versions were sold under the curious name of Wealemefna.[3] Writing in 1881, Morris described how he had created a wholly original name in an attempt to outwit his imitators; he also refused to disclose the origin of the word.[4]

The other opsiometer I have was made in Germany and I will make a separate post for it.

Thanks for looking,
Dave