60's Mecr 4 Cyl Distributers

Question for Merc experts. I've got 3 50 hp Mercs, a 65, 68, and a 70. The 65 has a simple stator/rectifier charging system, with a Mod 4D-5 distributer. The 70 has no stator, no charging system at all, and again a Mod 4D-5 distributer. The 68 has me puzzled. I can't read the dist no, but it has different wiring from the 4D-5 , which only has one wire going to it (ignition ground/engine shut off?) It has a large switch box? under the front cover support, and a large orange circular electronic part off to the right side of the cover. See the pics. I also have a spare dist, a Mod 4D-4. What are the parts on the 68, and is there a major difference between a Mod 4D-5 and 4D-4 dist? Are the 4D-4 and 4D-5 interchangeable?

The one on the right(with the yellow cap) is points-less, all electronic. The others use points.

Jeff

So they went from points, to electronic, then back to points? Or could this have been a retrofit?