J M Noeding wrote:
have been examining some surplus mobile telephone base station
equipment and discovered that the 70MHz to 455kHz mixers consists of
2x SA602. Since I've never seen an application using two such items,
my guess it for an image rejection type mixer.

An image rejecting mixer requires quadrature inputs (both signal and
LO), two mixers, and summation of the outputs i.e.

sin(A+B) = sin(A)cos(B) + cos(A)sin(B)

Also - you're unlikely to have image problems at the second mixer.