The M109 self-propelled Howitzer gun, known by IDF as "Rochev" (Rider), entered the Artillery forces' service before the Yom Kippur War (1973). In that war, only one battalion was equipped with these guns, the "Tiger" battalion.
With the time, IDF M109 are upgraded and from this program born the Doher that share the same hull, turret, barrel, engine & transmission of the Rochev. Some improvements of the Doher are internal and can't be seen from the outside: Inertial Navigating System (INS), air filtering system, and some changes in the driver's panel & cabin and NBC protection added.
But the external, visual differences are two sub machine guns on the Doher's turret, only one in the Rochev. The additional SMG is positioned near the sight ballistic shield. Electrical travel lock (known in Hebrew as "BiFoot"), external generator, different commander turret and others.