Cleaning DME contacts

[OldHead-MKV-Owner]

Just shipped my stock and donor DMEs to EPC to Femto and then they'll be coming back. I noticed the electrical contacts on the stock (manf. 12/21) DME are significantly cleaner (less oxidation/corrosion) than the donor (manf. 03/19). I get that there's almost 3 years separating the manufacturing dates but they looked night and day different.
when I receive them back, should I clean the contacts? The EE in me says why not. Just not sure if there's some weird coating or just something else I'm missing with these DMEs.

I did search this but couldn't find anything. Any help is appreciated.

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[OldHead-MKV-Owner]

Pics of the contacts. Wish i would have taken better ones before shipping out. First is the stock DME