Vintage 1950’s Aviation Fighter Pilot’s Intercept Plotting Knee Board FNA-340A; question about use and documentation

[VBF-12_Stele]

Hey folks. I came across this item at an aviation museum in Palm Springs. They had a bunch of them for sale at the table; I got one for $13. The volunteer/veteran told me there should be documentation on it, but I've looked all over and I can't find anything that references it or any documentation on how it would be used.

 

The back of the board has a plate that reads:

 

U.S. Property

Intercept Plotting Board

MFR'S Part No. FNA-340A

Cont. No. N383-61244A

G. Felsenthal & Sons, Inc.

Chicago 18, ILL.

 

I found the item listed on ebay here. It looks like a reproduction of an old tool, but I can't even be sure if it was something ever made. If someone can help me figure out what this is exactly and how its used I'd appreciate it. ?

 

https://www.ebay.com/itm/Vintage-1950-s-Aviation-Fighter-Pilot-s-Intercept-Plotting-Knee-Board-FNA-340A-/252410519457