Need information on this tool

Found this in a friend's warehouse. He has a lot of early parts but he didn't remember what this was used for.
Looks like it is to set spark or timing on a V8 ford.
Any information is appreciated.
Thank you.

 

Looks cool.... Here's a bigger picture of it....

 

It tells you when the points break open. I made up a light that for my Model A.

 

Thank you 1930artdeco for the help with this.

 

Sweet!! Another tool I don’t need but want now!!