Hmmm!
Is it a magnet? Could it make a sound? From IPDB photos that thing is not in any photos of Flipper. Could it be from another earlier or later card themed pin (I don't know).
There is a hole just below the left flipper, does that black block have any part that could of been up through the hole? Could it had a part that moved that stuck up into the playfield? Can you determine what it is wired into? Could be wired into the Tilt Circuit?

North America, evening Bump.

The IPSNDB shows a few 1960 Flippers with a 'G' in the serial number, either at the end, or in front of the number. That 'A' is a mystery. Most serial numbers in this era use the initals from the game.