I almost posted this in the long Libyan munitions thread, but I decided on posting a link there to this thread, and having a separate thread unto itself since mystery munitions are a little more deserving of more attention to ID them.
This comes from a series of articles, and is probably reported on elsewhere about the long and difficult attempt at identifying an unknown cluster munition that is delivered via 122mm Grad rocket. It looks similar to the American M77 used in the M26 MLRS, but that is about all anyone can say. The suspicion is that it is either a Chinese or North Korean rough copy of an M77:
A strange looking fastener on the underside of the lid here?: