It is a factory issued, Saco Defense USA made, Stainless Steel Mark V, circa late 1990.s early 2000's.
So is the .340.
These are, in my mind, the most desirable all weather Weatherby. True stainless steel, as opposed to the current silver-coated carbon steel Weathermark; stainless steel machined metal bottom, as opposed to the 'pot metal' cast current bottoms; solid barrels, as opposed to the current fluted, light barrels.
Both the .257 and .340 shoot ~1 MOA with a variety of loads: 100 gr TTSX, 100 gr Norma Spitzer, 225 TTSX, 250 gr Nosler Partition.