25-35(WCF) was a caliber I have read that Krag varmit rifle conversions were done up into.
To further confuse things, could the rifle in question have been marked 25-35 Remington?

The 25-35 Remington marking actually represents the .25 Remington Autoloading Rifle (Model 8).
Early on in it's production Remington marked the 25Remington caliber Model 8 guns as '25-35Remington'.

If the Krag was surely marked 25-20 Remington,,disregard!