A guy at work has one of these (from when he was a kid), and he asked me to try to fix it. After futzing around with it, some cleaning and a very generous oiling was all it needed... plus a little filing on the feed mechanism.
Anyhow, I've got it working fairly well, and shot a couple of cartridge's worth of BB's through it. It really is a pleasant gun - fits the hand well, balances well... and it has an absolutely TERRIFIC trigger for a double-action BB gun! Light pull, really crisp let-off, and short travel.
There's no valve hammer to cock back, it has an "elevator" that lifts the BB up to the barrel and releases the gas valve when you pull the trigger. Obviously it's a farly robust mechanism... it still works despite 30-year-old seals. It clocked at around 440fps, and got about 100 shots from a single cartridge.
So what ever happened to this mechanism? It's far superior to ay other double-action steel BB or gas airsoft pistol I've tried... and even better than some single-action. it is a real joy to shoot. Any clue why it went away?