I do know the true Keith bullet is square grooved ,the round groove is a Lyman change to get it to drop from the mold better.I`ve also had input on this pic saying the narrower/smaller dia. front band was to address chambering woes (the band was larger than the throats of the cyl causing a balking issue)
Yep there was a LOT od discussion over at CB's on this very subject. When I was first looking into MP molds, I did a few searches and found that a few of the folks who were instrumental in bringing out some of the H&G original design type replica's, were also wanting them to be as close to the original Keith SWC designs as possible. How close they actually got, I personally dunno, but the final resulting MP molds that I already have sure do throw some awesome bullets.
One of the main reasons I went the MP route was that you also usually get at least one choice of HP pin with the set, as well as the molds are brass 4 cavity. I had already gone the 1 cavity Lyman route and while functional, after pouring several hundred up using the Lee 6 cavity, well you can easily see, I was more used to production than what I was getting.
Another one I am growing VERY fond of is the MP 452-640. With the SM HP pins I get bullets for my 45 Colt and using the large I get some heavies to use in my 45 ACP. While I am not feeding it a steady or even regular diet of them, I have found they shoot excellent, and after a bit of head to head testing against some top name JHP's I will now be keeping them stationed for home defense. From what I saw when I shot them up against the others, there is absolutely no doubt in my mind that any BG will definitely rethink any ulterior motives.