provenance; or perhaps "acceptance" is a better term?
If I hand you an American Silver Eagle, you're probably going to be able to evaluate it and make a reasonable determination if it's real or counterfeit, likewise for a Sunshine round. If I hand you a totally unknown round, you may be less willing or unwilling to accept it.
Obviously the above statement is very situation dependent, "you" could be an individual I'm trying to barter with, a coin shop owner, a private dealer, ??? You may have access to scales, acid, comparison coins, years of experience...