When I started out making models I found I needed tools I didn’t have & couldn’t afford, so I made them. I continued to make more tools on the principle that, sooner or later, I would have enough for the models to flow from my workshop in large numbers. Didn’t work! Now I just make tools for the fun of it. So when this extremely rare surface gauge (in fact there is only one known to have survived) was posted on an internet bulletin board I just had to have a go.
The tool was patented in 1889 by Mr. Carl G. Osterman, this example is marked with that date and "Manf'd by A.A. Vose"

The adjustment of the scriber is by worm and worm wheel driven by the top knob and then locked in place with the side knob.

A search through the scrap box turned up a suitable piece of cast iron and using computer photo editing software I was able to draw a profile of the body from the original image, it only required a small alteration to fit around the hole in the cast iron. This was milled & filed to the profile.

The worm wheel was made from brass, hobbed with a ¼ BSF tap & a worm screwcut to match. The wormwheel is keyed to the locking shaft with a 1/16” key.

With the body set up on the lathe faceplate the recess for the worm wheel was bored. Next was the trickiest bit - to drill the hole for the worm, ensuring a good fit for the worm on the wheel. There is no adjustment for this so I was quite pleased when the hole was drilled & the worm & wheel engaged sweetly, just requiring a little lapping in with metal polish. It is held in place by two 3/16” x 40 nuts. My fall-back position would have been to turn up an eccentric bush which would have allowed a certain amount of adjustment. Fortunately this was not required.

The remaining components were plain turning, knurling & a little hand turning to finish off the knobs. The scriber is of 3/16” silver steel, hardened right out at the points.
My thanks to ‘Bill’ in Kansas City for posting this tool originally, for giving me the information that enabled me to make a copy and for posting other interesting tools that have kept me busy in the workshop !

After I had finished the gauge, another contributor to the same website kindly posted the patent which can be found here: "www.pat2pdf.org" No. 396109) so I was able to check my guesses against the original. The only major difference is that in the original the locking shaft & worm wheel are one piece as opposed to mine where the wheel is keyed to the shaft. The patent also shows another height gauge with the worm and wheel adjustment, but fitted to the more usual vertical bar.