What is a Folmer Graflex gravity-type synchronizer? What is it used for? I bought one because it was in a nice wooden box. I found none on eBay and no information anywhere else.
It tests shutter sync speeds.
http://www.radionerds.com/images/c/c3/TM_11-2378_1944.pdf page numbered 1
I doubt it has much use today.
Here's a link to the user manual for one: http://www.cameramanuals.org/prof_pdf/graflex_flash_synchronizer.pdf