One additional note to add to my previous post:

I read on some other "Sigma info sites" that "S" sometimes can mean "spruce" or "solid". Apparently it can depend on the guitar's appearance itself (when you get down to it), as some variances in the "letter model's meanings" I have read could fluctuate as a result of different countries of manufacture over various years.

I am convinced that the SE-19 that I have is sapele wood (as I mentioned in the previous post), and here's why: I've seen guitars with "spruce" wood---my SE-19 looks nothing at all like spruce. The wood of my SE-19 is very characteristic of sapele---it is a reddish-brown wood, with the grain having the characteristic "interlocking and changes in direction in frequent, irregular intervals" (http://www.eastteak.com/products/finehardwoods/sapele_data.html ). This would explain why the guitar appears to what I call "shimmer" and change wood tone color depths, depending on how the light hits this unique grain at various points. All 4 sides of this SE-19 are the same exact wood: sapele. The only contrasting wood is on the bridge support and in the decorative "Native American-looking" stripe I had mentioned that goes down the back (as well as of course the fret board and front of the headstock). Everywhere else, it's the same reddish-brown, intriguing grained wood.

My only confusions are these: a Wikipedia article on Sigmas stated that the SEMC-28 had the "arched back" (I realize that Wikipedia can be wrong on many things, however). My SE-19 is stamped (as I stated above) on the inside bracing as an "SE-19"---yet, the back of it is slightly rounded (not sure if this would qualify as an "arched back", as it certainly visually appears to qualify for such)---is it possible my SE-19 is actually an SEMC-28 and was stamped wrong? Or is Wikipedia wrong? Is the SE-19 also an arched back and Wikipedia just failed to mention that feature for the SE-19 as well? These are just a few of my questions.

Furthermore, my SE-19 is a cutaway (a thin-bodied acoustic electric with the cutaway as described in my previous post). The SEMC-28 (from what I understand about these letter codes) is also a cutaway, as the "C" apparently stands for "cutaway"? This further makes me wonder if someone stamped my guitar incorrectly as an SE-19 rather than an SEMC-28. I would certainly think, however, that since Martin inspected these guitars before sending them out to the dealers, they would have caught any possible "mis-stamped" guitar in their inspections, if a "mis-stamp" were the case. I don't know.

The only way I would know the differences in these guitars is if someone knows a lot about these 2 specific models, or I had a picture/specs of the SEMC-28 to compare my SE-19 with. Anyone that has any comments or solutions for my questions, I greatly appreciate your help;)   I don't think I can email Martin, as they state on their site that they don't keep serial number records for Sigmas--so I highly doubt they would have kept specifics such as these on record, or the number of how many SE-19's or SEMC-28's were actually made.

Many thanks to all who have contributed history and information here--I've found it all extremely helpful;)