Probably been in there since the timing gear broke 25 years ago.

Not a worry. Cool souvenir though :)
--
-Matt I ♥ my ♂

For what it's worth----I recently purchased a new set of metal gears from Rockauto (mfg. by Cloyes) and had to return them due to quality issues. The steel crank gear had sharp burrs on the ends of the teeth, and the alum. cam gear had deep gouges or scratches all around the outer edges, on both sides. It looked like they skipped a final machining or finishing process. They were very apologetic & gave me a refund. In the meantime I located another set (fiber) so will be using those.

Tough to see in the photo, but it's likely a chunk of the timing gear.
Now, try to figure out if it's from the current gear or one of its predecessors.

If you're not sure, change it. There is no given time that a broken gear will last. Fortunately (sort of) the B18 or B20 is not an interference engine and will simply quit when the gear finally gives out without causing severe damage. But that could ruin your day.

It's not terribly difficult to change if you're relatively handy with tools.
You may consider going with a metal gearset as an alternative to the fiber gear. That's not to say there is anything wrong with the fiber gear, it's just that they're getting to be almost the same cost as a metal set.

Oil pump or distributor perhaps?