If you like the look of it the way it is, then leave it alone. I usually do not clean chips with molds as older chips don't look "right" cleaned. With the near new condidition your chip is in, getting rid of the dirt would only enhance its appearance.

Of course this is only my opinion. I assumed I am about to be ridiculed.

BTW, I know for a fact, that some collectors with some of the best collections in the world (with individual chips in the 5 figures) clean chips on occasion.

I just finished cleaning the once grimy Club Forest pictured below.