Anatomy of a Dress: Swingin' Easy

Another dress from my little bundle!  This one is Swingin' Easy from 1963!

The dress arrived a bit crumpled and smashed flat, as one might expect from a squishy packet sent through the USPS.  But a quick wash and press later, and she looks like this:

Quite lovely, no?  But equally nice is the back view:

I love that open back.  It's daring without being risque.

But now let us delve into the nitty-gritty.  First we'll take a look inside the bodice.

Unlike the Suburban Shopper dress, this one has a bodice made in four pieces: the bodice and sleeve fronts, two bodice and sleeve backs, and the cummerbund.  Yes, that means that there is a seam going down the top of each sleeve as well as one along the underarm!  And this time the bodice does have an obvious facing.  But, surprise, it's made of netting!  Which means it's practically invisible as well as adding no weight.  The netting is all one piece, and varies from 3/8" to 1/2" deep.  It's topstitched down, and beneath it the fold over of the fashion fabric is a mere 1/8".  Two small darts above the cummerbund give bust shaping; the seam allowance is 3/16", except at center front, where it's almost nothing, so I'll have to keep an eye on that; if anything's going to give way, it's going to be there.  A snap on the cummerbund fastens the garment closed.  The skirt is a full 20.5" gathered, again, onto a 4" waist.  The ribbon ties are 3/16" wide and 6" long.

Looking at the sleeve cuff, it looks like the top sleeve seam was sewn first, then the sleeve cuff, then the underarm seam.

This time, the hem was finished with an overlock stitch and possibly sewn to the dress at the same time?  I'm not as familiar with overlock machine capacity as I could be.  On the right side of the skirt, the seam shows as a line of prick stitches.

What I find curious is that on the upper part of the skirt seam, the seam allowance is 5/8" wide, folded under 1/4" and top-stitched down to finish it.  Then it simply cuts in to 1/4" wide and raw edged.  While I can understand finishing the part where the skirt is open and being handled, why not just simply do that for the whole length of the seam?  It seems like it would save time.  Though, I guess, it would add bulk at the hem....