Different Air Box cap

I just bought a 1977 KZ650C1 that came with a different air box cap.
I wonder if anyone has seen this type of cap on their early KZs?
It does not show on any 650 part diagrams.

Rob, that is an original airbox cap but not original to a 650. What you have is a cap from a KZ 750 B the twin cyl. that somebody used as a replacement. Nice find on the bike.

No eBay APP ID and/or Cert ID defined in Kunena configuration

The Gringo wrote: Rob, that is an original airbox cap but not original to a 650. What you have is a cap from a KZ 750 B the twin cyl. that somebody used as a replacement. Nice find on the bike.

Good call!! Here's a pic of on on the airbox:

Thanks Andy, and Ed, for helping clear that up.