This is a three part question from the two pictures
what is this device / It reads bosch the date July 29, 1924 and adjust less or more
what is it
how should I maintain it? Such as will the web strap disintegrate ?
Then you can see from the developing undercarriage corrosion, how should I treat it now to fix it ?
Try this place.
It is an accessory snubber shock.
Hard to tell from this picture but is the frame rail cracking away from the rear crossmember?
Looks like a stress crack forming by the weight of an accessory bumper or tire rack?