The 1200GR I got used about 6 months ago came fitted with a Jelco armboard, seeing as I had a 750 arm I just put that straight on. Now I've decided to give the original arm a go, so that involved removing the base, then removing the Jelco Ammonite Armboard (these are lovely items), and putting the original arm back, it had a earth wire on it which I take it is attached the chassis at any convenient point (I put it on one of the 3 tonearm base screws. Now I just need to put the counterweight on the arm, and am just wondering do these push straight on or twist on? Has anyone compared the original arms with Jelco 750 or 850?