Terrorist and insurgent organizations have used Mauser rifles. One such example would be the Irish Republican Army under Michael Collins, which received shipments of Gewehr 98 rifles from Germany during the First World War. The K98 saw used in the aftermath of the Second World War, in arenas such as the Greek Civil War and the colonial wars in Africa which ensued afterwards. We also captured some K98s (as well as Mosin-Nagants and Lee-Enfields) while I was in Iraq - the rounds they fired performed better at long ranges than the 7.62x39 round the AK rifles use.
A Gewehr 98 is a bit longer than KAR98s and K98s. The Gewehr has a different bolt than Karabiners. It is pointed horizontally, while Karabiner's bolts are pointed downwards. As for K98s and KAR98s, it will take a professional to figure that out. Also, KAR98s were produced after 1935, and Gewehrs were produced before that date.
There are few German Mausers.. The main one is the K98 . This was the main issue weapon during WWII. During WWII one of the places K98s were built was in Yugoslavia. The folks in Yugoslavia learned how to make them. After the war they took and redesigned the K98s and designed and made their own models.... They used them in their own army after the war and sold them all over the world. The M48 is my favorite yugo Mauser .