Not all of the NACS have been reported or listed.
Rare in an area [not out of the question] for a Frequency to have multiple NACs
either good reception from different sites, or software latency from a prior Hit/Intermod/Image
Please update your profile to indicate your Location, so we don't have to search and search and guess.
Based on past postings, I am going with Houston.
Houston having been home to many Major Events, some of them NSSE [Sporting etc] has seen different NACs appear
Lock on it, see if CLR or ENC and what you can determine is the use.
NOTE - if an active Surv - wait a few weeks before sharing
NAC 59C AND NAC 167 ON 170.8375. I do not see 59C for Federal on RR.