1) Cardboard matchbox sleeve with print directly on the cardboard (may be unglued)
2) Not yet glued cardboard semi-product for matchbox sleeve.
The shipbuilding term "skillet" initially reflected the form of unglued (or not yet glued) sleeve
Strictly speaking, skillet is not a label as the art image is printed directly on the box. It should be treated as a separate kind of phillumeny collectable (as matchcovers).
Nowadays most matchboxes (indepently of size) are made by this technology.