Thanks for the pics. They are just super. You got a nice find there.. I just have not seen that many 1952 and 1953 marked kits out there.
Nice collection of all three milled selectors!!
i believe that the rear stubs on most kits were mixed (not that it really matters). In this thread (viewtopic.php?f=20&t=158434) you will see that Cobra has all the wider/larger grip nuts, which clearly belong on earlier rifles.
I will be changing the chart below for the heavy top cover to reflect 1952 instead of 1951. Looking at the numbers stamped, I feel certain that they are original and not stamped later on. (however I have seen a pretty convincing T3 top cover matched to a 1951 receiver)
The fluted pistons do show up. If you choose to switch out the smooth shaft with Matt/Turbothis fluted pistons (after it is chromed), it will be pretty hard to distinguish, if at all possible. I have gone that route and it also adds another the cursed 922r part.