It's a 1942 Turkish K.Kale Mauser long rifle. The K.Kale's are domestic Turkish produced. Yours looks to be a very condition with the original Turkish walnut stock. The caliber is standard 8mm (7.92x57). Non-matching bolts are very common on Turkish Mausers. Value in today's market with the bayonet and scabbard I'd venture to guess $150 to $190. The sling is of course not Turkish. If the barrel condition happens to be excellent you might be able to get a little more for it if the right buyer is found.
"A life spent making mistakes is not only more honorable, but more useful than a life spent doing nothing."
George Bernard Shaw