Strange Brown & Sharp steel rule? What's it for?

[bigcaddy]

Since I by lots of machine tools on weekends, I sometimes end up with a large backlog of tools that need to be sold

I'm quite familiar with the tools since I use them on a regular basis but this one has me stumped.

No model numbers and it's rather hard to made sense of how it's used

 

[bigcaddy]

This pic is one of the ends

 

[Snap_cap]

Looks to be some type of engineers scale. Maybe it was/is industry specific?

 

[Kevin54]

I've never seen anything like that before. I used to have an old B&S catalog, but I don't know where it is at anymore. It's definitely an interesting piece, that for sure.

What is the total length of it?

 

[larry_g]

I would call that a scale, similar to an architects scale. If you have a map or drawing that is scaled to 30/32../38 parts per inch/foot/mile or whatever. Put the nearest whole mark on one end of the measurement and align the small scale mark to count the nearest fraction.

lg
no neat sig line

 

[PBCampbell]

Maybe a "gear rule"?
http://www.practicalmachinist.com/vb/antique-machinery-history/what-brown-sharpe-scale-used-115054/
Yep, that looks like it.
That's a really old piece!