Shopdog,
MANY thanks! That detail about there being a seam under the spring was very helpful. Your first and second pictures , when enlarged, appear to reveal a seam at the midpoint as well. That line at the midpoint is too crisp and uniform to be mere coincidence - IMHO. The photos, drawings and other details were great!
If any of you others guys/gals out there on the Forum have different models and variations, please share with the "tribe". As other chime in, I am sure that we will collectively have a better understanding of these seemingly simple (anything but!) accouterments from another era. Again, Shopdog, again a big thank you for stepping up and sharing so much with all of us.
J.B.