Hmmm... a bit of a puzzler with just that amt of info. The 12,7mm base and 14mm rim kind of limit the range of cartridges it might be, and 'straight case' with .420" bore (I'm guessing you mean groove diameter) and "about 2 inches" further complicate matters. If it were oh so slightly necked I'd bet on the 10,75x52R Mannlicher (Dixon _European Sporting Cartridges_ vol 1 pp 138-139) as it's about the right size and was popular until the early 1940s. Lacking a chamber cast basically there's no way to tell for certain.
