The other morning on the way to open the front door at work I saw a small electronic module on the street. Not a bomb, just in case anybody was thinking that, I know what that looks like, but a small flashing LED unit from a bouncy children’s toy. Still worked, just no ball or outer plastic clear casing, and 2 very flat CR1212 coin cells still powering it.
On the round thin double sided PTH PCB there is a COB, covered with white epoxy so as to match the top and bottom white silkscreened board. Nothing special, it is a timer that turns on the LED's for a few seconds after a trigger pin, attached to a spring vibration trigger, is pulled to 6V. Interesting is that the Little 2 pin 3 colour LED's have a small sequencer inside, and they match pretty closely for the few seconds they are powered.
This is a view of the small square LED, showing the small Ic inside, the wire bonds to the 3 separate LED died on the other lead.