Digital LED clock from G&C Supermarket on eBay.
This is a really neat little kit I got for four dollars from aforementioned eBay store. I do not recommend it for those wanting to learn circuitry or micro controllers as it doesn’t come with a schematic or source code. In fact it isn’t supplied with any manner of instructions, builder or end-user.
My plan of dumping and disassembling the microcontroller firmware ended abruptly when I found out that the Atmel AT89C2051 is not the AVR architecture to which I am familiar. It is instead Intel MCS-51 architecture. By studying the PCB however I deduced that the button debouncing must be implemented in software and the time keeping interrupt based on an 8 bit clock divider and 8 bit counter. ( 12,000,000Hz Crystal / 256 Clock Divider / 125 Counter = exactly 375 interrupts per second. )
At some stage I want to replace the AT89C2051 with the pin-compatible ATtiny 2313 or 4313 and write my own AVR architecture firmware.
FYI: the beeper on this is loud!