forerunner

noun5

1. •
   A runner at the front or ahead.
2. •
   A precursor or harbinger, a warning ahead.
3. •
   A forebear, an ancestor, a predecessor.

   • Bakelite is a forerunner of today's plastics.
4. •
   By extension, a non-competitor who leads out the competitors on to the circuit, or who runs/rides the course prior to competitor trials, usually testing or checking the way.
5. •
   A postage stamp used in the time before a region or area issues stamps of its own.