Technical Unknown Stewart Warner Vacuum Gauge tester??? Need info HAMB'rs

To anyone who takes a moment to read this--thanks.. Nothing super entertaining here as I'm seeking information on the item shown in the pictures below. I posted this over on the GarageJournal.com seeking information and the only possible explanation thus far is some sort of vacuum tester for old vacuum fuel pumps, or something of the sort. Either way--I don't really know and I'm just seeking information. Please PM me, or feel free to post here on the thread for others to be educated as well.
Thank you in advance--

 

yep, thats a vac pump test set

 

Looks industrial to me,,,,,,,,,what's on the tag?

 

It's for testing the Stewart vacuum tank fuel systems used in the '20s