Re: C&R 338 lapua
About the only one you might find would be an early .338 Winchester Mag.
(Designed in 1958) The rest of the herd (.338 Lapua, .338 Federal, .338 RUM,etc.) are all too young to meet the C&R 50 year requirement.
There's always the chance that you might be able to get one specifically declared as C&R, but that's pretty much of a one-off situation.