The Curious Case of the Corona 3

Recently I acquired an early Corona 3, one of the ones with the front plate reading (Standard Folding Typewriter) and the front bar reading Standard Typewriter Company, and having ball bearing type-bars (Which I would like to mention seem superior to normal segments). 

As is my standard procedure for incredibly dirty machines, I began proper dissasembly to allow a thorough cleaning. First, however, I checked the serial number on the carriage, having not found one in the normal spot on the body. 38,761 it read, much to my glee. But there being no number on the body confused me, until I remembered they are stamped on the actual underside of the body, on the rim. And indeed, there it was. 47,152. I, through some serious investigation and lab research, ended up concluding that the two numbers were indeed different. And so that brings me to the first curiosity I'm to ponder.
(Update) I've just read through the newest edition of ETCetera and found that all the early coronas with the subtitle have a difference of serial number. One curiosity down.

Which serial number truly represents the machine?

I can only surmise that the body serial number, though being higher, is the true representation of how I should go about identifying this machine. The body of the machine is its base, after all. But what do you, fellow typo-spherians, think of this issue?

In any case, it means this little machine was (I can assume) at one point rebuilt to some degree, early on.

Later, as I began to clean the type-bars, I noticed the second peculiarity;

After once more engaging in research never before seen, and after consulting the leading experts in the fields of the language and grammar, I was shocked to learn that periods and commas are not the same thing. Nor are commas exclamation marks or vise-versa. Shocked, in utter disbelief, my entire universe tossed into turmoil. And more importantly, I stumbled into the second of my curiousitys.

Why does my machine have a key for periods only, yet the type of a very early 3 bank? (The period/period/comma can also be found on Fox portables. Never forget the Fox.)

Again my conclusion is that the machine was rebuilt at one point, but surely any sane individual doing so would recognize that you cannot type more than a sentence without realizing it just keeps being comma'd, rather than being allowed to end at long last with a period.

If you have a theory on this awkward inconvenience, let me know. How people ever were ok with shifting to end a sentence... well, we've clearly evolved as a society. I'll say that much.

End Note: What a little tender loving care wont do. These didn't even look like they were plated at first, they were so filthy. (Top one is for reference.)