[StormEye]

The Thor-Agena rocket "skin" has a very smooth, aerodynamic surface.
I'm sure there's probably a rivet some where on the rocket -- but not very many.

The comparison shows that the North Koreans lack welding know-how and modern welding technology. It would be a good idea to keep them from acquiring it too! Nevertheless, the NK rocket did launch, travel quite far, and managed to place their primitive "satellite" space junk into orbit.

[NorthMountain]

lack modern welding technology

TIG dates to the early 1940s.

It would be a good idea to keep them from acquiring it too!

Yes. Even a simple Lincoln MIG welder from Lowes.

to place their primitive "satellite" space junk into orbit.

An orbital launch vehicle is also an ICBM.