Gareth W-B owns one, or one of his family do. It was a simple re-hash of an earlier Diana break-barrel, fitted with an exciting black stock and faux silver 'receiver', giving it the look of a small semi-auto .22 rimfire like a Browning or Remington.
They might have been smooth-bore for use with darts, and I imagine few are left as they were junior guns for kids, thus having a short life-expectancy.
Good marketing idea and a pretty little gun, although bordering on the toy-like. Not many little guns like this made today, nearest would maybe be the vastly superior HW25.
Here is the spec from Walther's book...
Mibro Diana G85/1 Bob Cat
Appeared in 1978 ... clever use of an obsolete design, the Model 15/G74, with which it shares the barrel liner and cocking lever lock-bolt. 2-piece cast alloy receiver contains the air cylinder ... simple trigger... shapely wooden butt ... too long for many juniors.. plastic ramp mounted blade and adjustable rearsight.. efficient auto-safety. Average accuracy but has advanced features making it among the best in its class (sic). Weight 3.7lbs.