MK-1 will MK-2 or better yet MK-3 magazines work in it?

have a 1981 or 82 MK-1have had for 25 years will the MK-2or MK_3 magazines work in it ?

Not sure about the II's but I'm sure the III's won't work.

I am almost positive the MK I and II's can be interchanged. The Mark III factories will not, You can pick up after market ones from Majestic Arms LLC where you can interchange between MK II's and Mark III's I have a couple of these and the price is reasonable, and the quality good.

Shoot straight and shoot often
GF

I have seen videos on U-Tube where they modify the Mark IIIs to fit. I have not tried it yet. If I had both a Mark I and Mark III I might try it, looks like you could easily end up with a paper weight though. I am waiting on Ruger to get caught up again on Mark I mags to order a couple new ones. Mark II mags will fit, just might have to change the thumb button to the other side. Only real difference is Mark I mags are 9 shot with a chrome end plug, and Mark II mags are 10 shot with a black end cap. Replacement Mark I mags can be easily modified to 10 shot though.