Yes. The base plate.
However, for a small calibre projectile, the butt would probably do in a push.
There have been similar sized indirect fire weapons like the Japanese 50mm Type 89 Knee mortar of World War 2.
It looks grossly oversized for a standard grenade launcher, undersized for an AT weapon in the modern age, so you have to wonder just what all that barrel length is for.
I suspect that the NKs may have designed this thing as a multi purpose system to fire a wide range of projectiles, some in direct fire, some indirect. The original photo shows an exhibition table with two projectiles, one what looks like it has folding fins, the other with what looks like a basic spigot stick.