The rifle's checkering pictured looks worn and/or sanded more than anything.
True 'flat top' checkering is done with tools that do not cut diamonds at all, but instead straight incised lines. Very difficult to do and get a perfect job of it. There's no going back over the work to straighten up the line or move it slightly as can be done with diamonds. The first cut is also the final appearance other than depth.
The flat top diamonds commonly seen on American SxS's and some rifles is just common diamond style checkering not taked to full depth.
Part of the reason is that the checkering is usually of very wide spacing,,sometimes 12 or 14 lpi. To point those up means cutting very deep and then the diamonds end up looking huge and somewhat out of place. Plus it's faster to the end result to leave the work 'flat topped'(less $$) and more comfortable to the shooter as Mr Hallquist points out.
FWIW
I knew a husband and wife team of freelanse checkerers that did work for Winchester, Marlin, Colt, and just about any other firearms company in the CT area from before WW2 till the late 60's. Harold & Mildred Arthur.
Their checkering was never razor sharp pointed IIRC. Perhaps a result of the tools they used and the speed and production style work they were doing.
They used for the most part a carbide tool that was about 1" square but gently curved front to back. Machined to the appropriate lpi and equipted w/ a wooden handle to allow both hands to be used to work it, they would checker stocks at an amazing speed.
The tools were originally supplied to them by Winchester I was told, but later they found an outside source to make up some more when Winchester refused to make any more or supply the drawings for them. Even carbide wears out after a while.
Harold had originally worked at Winchester in the wood room before WW2 and that's where the connections to the work began.
It was factory quality and patterns of course, but that was their work. Everything from 21s,12s 42s to H/Standard and Colt grips, Marlins stocks,,,anything from anyone that needed checkering.
She was quite capable of 'one-of' custom work too and did do some of that. But it was the production type of work that kept them busy and making money.
Interesting folks. They never owned a house,,always rented,,had 9 kids IIRC. When the urge struck them and work slacked off a bit, they would take a vacation in Havana (till that was off limits!). I knew them from Pedersen Custom Gun Co in the early 70's.
