Hello there, it’s an early Amberg production Gew98 that was modified in the 1930’s with the updated rear sight and then made its way to Spain. Many were chopped up into budget minded Mauser sporters and imported, and marked 8mm like yours is.
Depending on overall condition, I'd say around 200, in my opinion. That's about what the last one of those I saw was tagged at. Depends on overall condition.
Yes 8mm, at least originally.