That appears to be a 3-pole jack with auxiliary switch.
Older stereo music systems typically used the jack socket switch contacts to switch on the internal speakers when the jack was removed. We can see this on contacts 5 and 2. The √ on 5 is the part that touches the inserted plug. When the plug is inserted the √ is pushed away from 2 so that the switch opens. It should be clear that the amplifier output would be connected to 5 and the speaker to 2. With the plug out the speakers will work. With the plug in the headphones will work but the speaker will be disconnected.
- 7: Sleeve / GND.
- 5: Tip.
- 2: Tip pass through. Contact is closed when unplugged. Inserting the plug disconnects 5 from 2.
- 6: Ring. My guess is that the black block is an insulated link which drives contact 4.
- 4 & 3: These form an isolated switch that is closed when the plug is removed.
3 & 4 have no contact with the audio and so could, for example, be used to signal to a device that the headphones had been plugged in and the volume be adjusted accordingly.
It doesn't have a second ring connection for a microphone.
Continuity check confirmation:
- No jack:
- 5 & 2 are connected.
- 3 & 4 are connected.
- There are no other connections.
- Jack inserted:
- Sleeve to 7.
- Ring to 6.
- Tip to 5.
- All other pins isolated.