The K number is I think an RYA issued registration number for cruising boats.
International racing numbers were changed some years ago because spectators were apparently confused why UK boats had K numbers. So British boats changed to GBR, which from any distance looks like Germany's GER. the Dutch became NED's, the Hungarians are all HUN's etc.
Dan
There was (is?) also the RYA issued 'Y' numbers for cruising monohulls and 'M' numbers for multihulls!. I thought 'K' was reserved for IOR Certificated raceboats way back, now replaced by GBR? All very confusing, Germany USED to be 'D' tpo but I have no idea what Denmark was.
<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>
These are nationality letters for racing yachts, and are prescribed by the International Sailing Federation (ISAF). K used to be the letter for Great Britain and during the same period West Germany was G. Most other countries had a one or two letter symbol.
With so many countries getting in on the sailing thing, the system was changed to a three letter system, so Great Britain is now GBR.
For anyone interested (and who wouldn't be) there is a full list of national letters in the Racing Rules of Sailing (RRS) Appendix G. The rules are published on the web at www.isafrules.com/rrs20012004startpage.swf