Antique Porter Counterfeit Detector Co Machine, used on U.S. Paper Money

Description

Porter U.S. Paper Money Currency Counterfeit Detector Machine
Chicago
This is a Porter Counterfeit Detector in Original Wooden Box.
Box takes a key to lock/open it.
No original key.
Will supply a key that you can wiggle around in lock mechanism to unlock if closes and lock it.
No original instructions with it, just a PDF copy from the web.
This detector operated on the basis of placing a genuine note on one sliding panel and a suspected counterfeit on the other, and then by manipulating the panels, the notes could be drawn into line on the alphanumeric graph, and the position of various elements could be compared. The original glass is etched with the graph lines. The exact date on which these were manufactured is a matter of conjecture, but materials and craftsmanship seem to indicate late '20s or early '30s.
The instruction sheets of this detector has an overprint export-agent name and address, which indicates that these were still being sold in the 1940's, as the agent's San Francisco address includes the two-digit postal-zone number, which came into use in May of 1943.
While there were lots of contemporary books and periodicals for detecting counterfeit currency, physical devices are rare.
Condition:
The wood case has lots of surface scratches & could be freshened up; the glass is not broken and is original; the knobs, screw, and moving slide is original and without damage.
No original key.
Any questions, please ask.
Note:
I’ll try to get it to ship with lid unlocked, but key can be used to unlock it if gets locked.