I have a mystery that needs solving. I have what looks like a transistor. It has three pins which should be emitter, base, and collector. The package is labeled A129. I have tested it with a multimeter using the diode function and there is voltage through no matter how I place the meter leads. I assume it's broken. But the mystery is that it alone makes at least a single LED blink at a constant rate.
I have it hooked up to a breadboard with DC power (was trying to use a capacitor and transistor to make a blinking LED and couldn't understand why it wouldn't work, lol..) at 3.3V. If I put it to 5V it does not blink anymore. Is it not a BJT?
Update - Photos added as requested: