This grenade came to the US as a war-relic with US troops in the 1950-1953 period.
A US Mk2 seems to have been used as a mold, but the grenade has a cast-on carrying lug.
The fuze threads are same as the Russian UZRGM, but it's a pull-friction type.

Francesco provided the sectional drawing shown on the right.
It came from documentation which named this grenade "A-3".
It is still unclear if it was really North-Korean. It might be
South-Korean as well.
On the South Korean page there is a similar grenade.

If someone has any more details,
Let me know at

Photos Cory.

Photo provided by Francesco.