Type J-1, Time of Run-Sighting Angle Computers - Theater Made?

[witriflyguy]

Just wanted to share a few photos of a new acquisition I received. I recently picked up a pair of Time of Run-Sighting Angle Computers, one looks to be theater made? The computer on the right is made of what looks to be photo paper sandwiched in between thin pieces of plexiglass and fastened with a small flathead screw. Have you guys seen any thing like this before? I know it's tough to find J-1's now, seeing this hand made version makes me wonder if they were hard to come by during the war, too?

 

– Dan