Any photos of this type?
Uh oh, looks like I may have confused myself in all of the excitement. Upon review, it appears that I got mixed up the variants/skis/markings combinations. In my folders, the ones with skulls and skis are all N.17s and the N.21 with skis has the roundels. The other variants I found with the skull & crossbones have wheels. Sorry for the confusion, but I'll look around some more.