Of all the criteria for determining Cokes, is there just one point that is absolutely conclusive?
Kinda, sorta, maybe, but no.
The larger checkering area is a feature of Cokes, but you better know what you're looking at before dropping $500 or more on a set of grips.
Real Cokes (S&W called them Special Oversized Target Stocks) were only made for square butt N frames, be made of Goncalo Alves (or possible rosewood), have a larger checkering area compared to regular target stocks, have diamonds around the escutcheons, have genuine S&W medallions and blued steel circle inserts on the inside.
Original Cokes compared to diamond walnut target stocks:
Custom/aftermarket grip makers do produce reproduction/homage grips that look like Cokes at first glance. Genuine S&W's are typically the only ones with circle inserts, but a skilled craftsman like magget44 could checker a set of real Presentation Target stocks and fool a lot of people. They would probably cost as much as a genuine set and might actually be nicer, since S&W stocks were machine checkered!
Repaired/refinished real Cokes:
Cullina Cokes:
Eagle Heritage Cokes: