I think I know what you mean by points. I don't know if there's a more informal terminology or not.

To my knowledge, within the NID line the points are not indicative of a particular interval of time. Field grade guns got three points, but then the next grade up, 2, got only two points but also got scallops and more lines per inch. Beyond that the guns got multi-paneled patterns, fleur de leis, more scallops, more lip and so forth.