Really really late model MRRs, as above. Kinda well-known for either not releasing at all, or blowing up into exactly 6,324 pieces when they let go.
A guy at my local shop calls them Exploding Mousetraps.
There's about 15 pairs of these on the ski-fence the city dump. Even though some are full-metal 20 DIN jobbies I wouldn't touch them with a bargepole.