Date code or something ending in "CT CO"
the sandy tan M-3060 ish piece you found with the date code is definitely a Victor product and not an NL it is rather rare to find victor pieces with dates but they do exist... especially the M-4800 the mar4king you found reminds me of the ones seen on the crowns of M-4800 units.
also the firing rest and crown characteristics are typical of victor pieces...
Or could it be VICTOR? It's a bit of a poor marking, but I think that could be it.