Develop an eye for factory work as opposed to checkering which has been refreshed. If the work has been very well executed it will be increasingly hard to tell. Doing that level of work should be your objective.
There were degrees of variation in the checkering. Each grade was not checkered identically. Variations in LPI and style exist.
Flat top is more durable so better suited to hard use than fully developed diamonds. You will see it used up to about 20 LPI and more on earlier guns
Absolutely uniformity is one hallmark of quality work.
Nothing is a more glaring tell of replaced wood or non-factory work than checkering that isn't absolutely identical on both forend and buttstock.
Checkering in a sunny window on an icy morning when it's too cold to be doing anything else can be pleasant work. Have fun!