nskaye,
Quite a few.
Bell 206: 17 single-digit S/Ns listed as still flying, the earliest being 206A S/N #7 (
N1368X), plus
29 more up to S/N #200 and
89 more up to S/N #500 (the last of the aircraft built prior to 1970).
Agusta-Bell 206: 42 aircraft up to S/N 8200 (i.e. pre-1970) still flying, the earliest being AB206B S/N #8006 (
EC-FCP).
...plus a shed-load of
OH-58s: about 230 pre-1970 aircraft still in civil and military service, the oldest being OH-58C S/N #40002 / 68-16688 (
N230FC).
Data c/o
Ascend.
I/C