Please help identify hardware.

Looks like you have a Benchmark bi-fold door. The 12" pins are unnecessary. I believe the person was using plain and threaded bar from an hardware store to make pins for the door. The threaded pivot bi-fold pin would be our 21-002, and you would need one per door. You would also need three 21-042 guide pins, which locks on with a push nut, or instead three 21-044, which uses a spring retainer. People like to use the 21-044 because it is easier to install and remove.