I only ever saw this series the first (and only) time it was broadcast in Ireland (remember the 'Spinning Coin' at the start ?). Anyway - I agree - it was an excellent 'Sting-in-the-Tail' type show - the 'mark' usually deserved what (s)he got - so in essence we were rooting for the 'bad guys', in the mold of Newman/Redford in the extremely excellent 'The Sting' - a film which NEVER grows stale.
And yes - this is indeed a show which appears to have 'fallen out of Television History' - others being 'Cool Million' and 'It Takes a Thief' - these made Saturday evening viewing (while growing up) a delight.
More please ( but DON'T remake them as movies ! ).
Enjoy !