MAG was a company based in (I think) Switzerland- any more than that I don’t know, other than they were bought out by Kubota in the late 1980’s and some of the cross-over Kubota GS series engines were labelled “Kubota MAG” for a while.
The timing on these engines was a lot easier than most because the coil/condensor/contact breaker assembly was all mounted together on a common stator plate, I think it was made by Bosch. The stator could only be moved a few degrees one way or the other and it was normally marked with a chisel point once bench set in the factory, so you could take it off and put it back with certainty that you would get it right. Points gap was 15 thou.
Sometimes we used to find the end snapped off the valves on these engines, so check both ends thoroughly. Some valves used to “neck” and the head would come off whilst others would have a horseshoe collet to retain the valve spring and the end of the stem would snap off.
Good luck, they aren’t as bad as a lot of engines!