I belive the old chrome base mags came in 2 styles. One with the button on the left and one with the button on the right. Both were 9 rds. Better, and less problematic are the Mk. II 10 rd mags. Just put the button on whatever side your gun takes. Just look at the mag well and you'll see where the button belongs, left or right.
In other words, buy Mk II mags for shooting, not the old chrome base 9 rd ones and save the old ones for show. Ruger Mk II mags can be had for 18 bucks brand new. Kinda be a pain if your standard and Mk I are opposed mag buttons.
