Some kind of glass cutter?

[stanley62]

These look like maybe to cut glass tube..maybe for neon?  No makers mark that I can find.

 Jim

[wvtools]

It is a gauge glass cutter.

[jimwrench]

 Now if you just had a gauge glass.

[Chillylulu]

Cuts from the inside if a glass tube, heat to break.
A lot of scientific glass is / was handmade. This would give you consistent lengths.

Tapping on the outside you could chase the cut along the score.

Incidently - (I work quite a bit of glass) - you don't want to score a cut and go to lunch before you  finish breaking the score. Glass starts to "heal" quickly, requiring quick work between scoring and breaking. It makes a big diffrence.

Chilly

[Ray Smi7th]

Hello All:
  My first post here after my intro. I am really enjoying this section of the forum and would like to contribute this to the query. I bought this one at a yard sale several years ago thinking it was used to cut neon tubing. I have a small collection of vintage sign equipment and thought it would make a nice addition.

[Aunt Phil]

Site glass cutter used to cut glass tube that shows the liquid level in everything from coffee urns to boilers.

According to the salesman it's the greatest tube cutter ever made.  According to people who have thrown them across boiler rooms they are miserable _(*%^^*^$##%^. 
Personally I just use a 3 cornered file to score the tube.  Pyrex tubes can be more fun.

[lptools]

Hello, Millers Falls made a very similar tool, a No. 218 Gauge Glass Cutter. Regards, Lou