Oscillator using capacitance of LEDs. When the LEDs turn off, it looks like they sink current backwards through the anode.
Close the switch to start oscillator. Transistor on the right will switch on and the LEDs will illuminate. Transistor on the left turns on and pulls the base of the right transistor down. The LEDs turn off and sink current through their anodes; which is coupled to the left transistor, switching it off and the right transistor switches on again.
I think that's how it works anyway
