http://www.globalsecurity.org/milita...m-1978-170.htm
It's a 170mm gun on a T-54
"The M-1978 (KOKSAN) 170mm self propelled (SP) gun, of North Korean design and manufacture, is probably mounted on a T-54 chasis, a Chinese Type 59 hull or a T62 Chassis. The 170mm gun has no superstructure, and it has 2 large spades at the rear. The 170mm (~6.69") gun itself is a previously unknown type, possibly Russian coastal-defence or ex-naval weapon. The M-1978 Koksan gun was first noted publicly in a parade in 1985. The Koksan is named after the city in North Korea where it was first seen by the West in 1978. The M-1978 version carried no on-board ammunition supply.
The M1989 KOKSAN is a later version or modified M1978 which carries 12 rounds on-board ammunition supply. North Korea used them in batteries of 36 vehicles & supplied them to Iran when missiles became available as replacements. "