This vehicle is built up from the AFV Club M107 175mm self-propelled howitzer kit. Other than the metal tracks, it's mostly OOB, though the distinctive markings are a special order from Decalcomaniacs. They say in Vietnamese "King of the Battlefield" and "Thunder," and were put on the barrel when it was operated by the Army of the Republic of Vietnam (ARVN). The gun was captured in 1975 near Hue City/Da Nang as part of the final offensive that led to the collapse of South Vietnam.
Interestingly, Vietnam later used these guns during its war with Cambodia, and retains them in reserve, though the need to replace the barrels after several thousand firings means they can't use them unless needed.