I’m going by memory, but wasn’t the 300 win different because it would fit in a “standard” length action(‘06 length) as opposed to a 375 H&H “mag” length?As jmr40 said, it's probably a 300 H&H Mag. In fact, I'd bet good money that's what it is for a couple of reasons. First, Roy Weatherby didn't develop his 300 Weatherby Mag until 1944 (according to my "Cartridges of the World" book). And second, Winchester didn't introduce their 300 Winchester Mag until 1963. Yet (also according to my "Cartridges of the World" book) Holland & Holland introduced their great 300 H&H Mag in 1925.
Obviously, I prefer my superb 308 Norma Mag (introduced in 1960) over all of them.
I know it’s sacrilege, but there is a part of me that wants to build a custom 300 PRC on a pre-64 model 70… but hey, I’d also like to drop a Cummins diesel from a dodge into a ford…
As to the OP, that’s a mighty fine rifle… I’m on of the younger(mid30s) set that loves real bluing and a pretty piece of furniture…