there should be elastic bands going from pleat to pleat, in m series and g series jackets betwee the liner and shell. this was the way originals were made. when the bands are in good condition they expand with movement, and contract when at rest, thereby making the pleats functional. most, if not all repro makers install the bands,, but if they are of poor quality or tired, they are pretty much useless. run your fingers up and down the liner on the back,, you will feel them.
Yes, the M-422/ANJ-3/G-1 types all have an elastic band 1”-1 1/2” wide, connecting the inner seams of each pleat at about mid-back level and hidden by the liner. It keeps the very deep pleats closed for a tidy appearance, but allows them to open for free arm and shoulder motion.
Any elastic - used or stored - dries out and with time and heat and loses its snap. This gives a jacket “bat wings” - pleats that stay open, rumple, and bag. Replacement is tricky. The liner must be unsewn, the pleats folded closed, and the distance measured from inner seam to inner seam to cut new elastic.
If you measure the old, slack band, the new one will be too long and the pleats will still bag. If the band is cut too short, the pleats AND the back panel will pucker.
Really???...In the discussion I link to there, elastic was mentioned only briefly. Some insisted it was down to correct cut (not explained), and even the part of the goat used in the gussets. Seems like an effort at mystifying, rather than demystifying. (I always try to demystify.)
BTW, if you do check your Caglecos, view yourself from the side in a mirror while wearing them. If the pleat edges bag out or rumple, yes...you have bat wings. (They don't look much like bat wings. Bats fold their wings neatly. More like you're wearing a backpack full of pudding under your jacket.)
If you know anything about tailored men's clothing (not a common interest around here!), the bi-swing and other pleated, beltback styles, were popular options in sportcoats and suits in the 1930s. They went thoroughly out of fashion after that, due to the skyrocketing cost of skilled labor. Now they are very rare, vintage or new.
Other styles included the inverted box pleat (a slit down the center of the back); the shirred back with lots of small pleats or gathers, which billows freely over the belting; and the back with several knife pleats (usually 5-6, top and bottom - sometimes with sewn-in creases, sometimes not).
All styles generally had a shoulder yoke to keep the pleating confined to the flat of the back. The military jackets, including the Army 4-pocket blouse, do not use a yoke.
^ My first experience with a bi-swing back was with a navy blue mod-acrylic light weight paramedic jacket that I wore as a young paramedic. It was a trim fitting jacket, so the bi-swing action really came in handy.
Now the next question: Does fit affect pleat closure?
Taking my G-1 & M-422A for test try-ons after regaining 15lb, the jackets are comfortable, tho snug at the belly. Elastics, which are older, feel modestly taut tho not snappy. But I notice the pleats stay open unless the waistband is pulled down. Is this to do with the snug belly? Some other fitment issue? What are your experiences?
...Or might I just need my elastics redone even tho they're not super droopy?