Thanks for your elaborate answer and (again!) providing a wealth of facts and details, which I've not been able to uncover myself - highly appreciated!!
About the military letter's 6 skilling endorsement.. I'm surprised as well. I haven't explored this area too much, but my general understanding is, that unfranked letters were normally "penalized" with +2 skilling in addition to the normal 4 sk. rate -while Feldpost was free of charge for sender and receiver. If it's not simply an error by someone in the mail-expedition, then I have no good explanation for this...
Being an SH collector with a passion for numerals, I regard a cover with 230 Høruphav as the "holy grail" (well... contested by a 214 Pellworm cover ). I'm a keen admirer of DKKW's excellent thread on numerals (dk-sh numeral collectors are well-equipped with the ArGeSH catalogue + that thread bookmarked!) and long before I became a member of this board, I have been wanting to ask, if someone has a picture of such as 230 cover to upload to the forum. DKKW makes a mention of two of such covers - my guess is, that there are very few, if any, besides those two in existence.