There are nut drivers made by Xcelite (and others) that fit
these knurled nuts. There is one model that's adjustable
by means of a sliding collar.
There is an almost identical nut used on the K2's speaker
jack, but with two slots to add "traction". Xcelite also makes
these.
73! Ken Kopp - K0PP
ElecraftCovers at rfwave.net
http://tinyurl.com/7lm3m5