Hmm. Sounds legit. Not so interesting on a mid-2000s production bike I suppose.

 

Well ,,,, I Bought mine new and the original cases have the writing on them from the fac'try. ( This is the original case that i had to replace after a boss cracked.) Suspect, as others have said, that these are pair numbers to keep halves that were machined as one , together during assembly.

Dan

 

That sounds logical! Mystery pretty much solved at this point. I have no prizes for ya.

 

I'd be glad to accept free housing for a week in Kauai...

 

Fair enuff, mine doesn't have it so I assumed it wasn't factory. Happy to be proven wrong.

 

Common request

There's a famous Hare and Hound race every Labor Day. Come on out:
Labor Day Hare and Hound Extreme Enduro | Garden Island Motorcycle Club, Kauai Hawaii

 

Writing on my bike seems to have been protected by a thick layer of crud the PO kept between the engine and the skid plate.

 

I'll be more precise. I've had mine from new and it never had that writing, from new.

 

Possible rebuild then, yeah.

 

IIRC, the 2014 Ninja 300 I had, the 2014 Ninja 650 I had and my current 2015 Ninja 650 all had/have some similar markings on portions of the engine casings and some other parts etc. The Ninja 300 was bought used with 300KM on it, with no declarations on it. Both Ninja 650's were bought brand new.