Great pin. Congratulations on the pick up. PBR is The Pinball Resource. One of the many great suppliers of parts for Electromechanical machines.
Your buzzing flipper may just need a clean or adjustment to eliminate the buzzing. Sometimes after all these years the contacts on both the end of stroke switches which switch the dual wound flipper coils from power to hold are dirty and pitted along with the flipper cabinet switches that you actuate with the buttons.
Worst case you would need a rebuild kit that PBR sells for about $50. Probably the one I linked below, but you can do a little Google searching and give a call to Steve at PBR to confirm.
There are many good resources on line to learn about flipper issues similar to what you are facing. Here are a few: