What you are missing is a light socket pigtail. Less than $5 at most FLAPS. Your socket looks like the pins slots are even. Which would translate to a single filament 1156 bulb. I have cheated in the past by sanding one of the pins off of an 1157 bulb, and using a double filament repair pigtail.
These repair pigtails slide in from the bulb side.
I believe he is showing the contact insulator end of the socket. You can't see the bulb end. Two sets of bayonets. Maybe he can post a pic of the inside of the housing. Tail light has one bulb. Tail and turn/stop.
