What's this piece of metal that fell out with my crank pulley?

[AndrewS13]

I'm currently disassembling my SR20DET engine. When I removed the crank pulley a half moon shaped piece of machined metal fell out. I couldn't find anywhere on the crank or pulley that'd it go. Does anyone know what it is and where it came from?

Here's a pic:
http://imgur.com/a/ipgu8SD

[e1_griego]

It's a woodruff key.

Goes on the snout of the crank pulley. Half moon side into the crank so it's just a small flat that keys the pulley itself.

[AndrewS13]

It's a woodruff key.

Goes on the snout of the crank pulley. Half moon side into the crank so it's just a small flat that keys the pulley itself.
Thanks. I couldn't find anything in the FSM or online

[jr_ss]

Keeps the crack pulley from spinning. Sucks to time a motor when the pulley has spun.