Late reply but here goes - thanks for the PM Nigel, I've only just found it...
The K9 started off with a metal body and this remained during its most popular lifetime in the 80's. The K5 had a conical tip as I now recall and the grey plastic mount. I caused a sarcastic chuckle with the Linn guys when I tried a K9 stylus in a K5 body mount and preferred it (silly dealer comment as the K9 was obviously superior and more profitable of course). That was it after 1991 or so, as the dealer I worked for lost the agency in the early 90's dealer purge (long story and more to do with arrogant boss attitude in our now long defunct business rather than lack of business and staff enthusiasm for Linn, but I digress). The yellow stylus assembly had a suspension tweak to improve stability and reliability a couple of years in, but the sound was always lively, keen and just a little bit ott sometimes, lacking the finer details irrespective of the arm it was mounted in. A very 'universal' cartridge though and worked in anything from a Dual 1019 to the top decks of the era, linn or otherwise.
I returned to working with Linn, Naim and Rega in the late 90's by which time, the K9 had the same plastic mount, grey painted body and grey stylus housing as the K5 and without a microscope, the only easy way to tell them apart was with the fine writing on the stylus itself. the sound by this time had been refined a little, still lively, but possibly 'sweeter' in tone due I suspect to the plastic body mounting. The price was rising though, but it still compared to the Goldring 10** series in a positive way.
To bring this shit up to date, I'd say one of the better VM styli would be more like it. The VM95EN has a lower mass naked diamond than the albeit well finished bonded 95E and if the arm is fully adjustable for height as well as overhang, one of the fine line or Shibata VM95 styli could be considered I suspect. At least the VM95 series look better on a K5/K9/K18? than the old ATN95E needle
-Edit- I don't know how the Goldring E cartridges have their stylus housings mounted. Do they pull down and off like the AT 95/Linn K models, or do they tilt down at the front and pull forwards to 'disconnect the key' as the AT91/Rega Carbon/VM500 and previous generation do?
Just to add that until recently, I understand that the 'Cymbiosis' recommendation for a K9 replacement was apparently the AT 520 at a ton or so (for those not able or willing to fork out for an Adikt) and this reportedly has better copper in the coil windings as well as access to the 540 stylus (check the Lowbeats site in German for measurements as well as sound bites on the full AT500 range). No idea why the AT530 wasn't recommended instead, but all of them reduced slightly in price recently so the 520 is now a hundred quid and the 530 is £159. I'm very fond of the previous AT120E, but accept this model prefers a very low mass arm if the bass is to properly integrate and although I love the slightly extra sparkle, some systems and phono stages won't. I gather the VM500 series are tamer in this respect, if still 'lively' as the K9 used to be and both 95 and 500 model ranges track at 1.8 to 2g - 2g being the recommendation for pretty well all of them I think.
I have a yellow stylus housing K9 with a knackered stylus and it sounds total shit in all honesty - all splatter and splash. One day, I'll get round to trying a new better stylus for it and one of the VM95 styli are earmarked as and when funds permit.