This is from a workwear brand called "Demander", but there are no details about the brand. There is no definite date, but the shape of the pockets and buckles, and the fact that the fabric used is 8 ounces, suggest that this is a 1940s bib overall. The shape is that of a typical overalls, but without the hammer loops and tool pockets on each hip.
It has one large separate front pocket and side pockets on each side, and the side seams are triple-stitched. In terms of shape, this is a common style of overalls from 1940-50.
There are two large back pockets on the back. There are no hammer loops or tool pockets on the sides.
flasher
A flasher attached to the right back pocket. The illustration of a farmer etc. is cute. The brand name is written on it, but unfortunately there is no information to know the brand.
tag
A paper tag with the size and shrinkage ratio. With overalls, the waist would be 31 inches, even in youth sizes for 16-year-olds.
front pocket
There is one pocket, but the flapped and unflapped parts are separated and a pen holder is attached." There is an embroidered tag with "8OZ. SANFORIZED" on it, which I think is something you can see on other brands from time to time.
side pocket
Side pockets on both hips. Both ends are reinforced with red cannulae. By the way, the buttons are for putting on and taking off.
back pocket
Back pocket on the hips. One letter stitching, but no sleek reinforcement on the back side, but decorative stitching.
buckle
The buckle is shaped to hook onto the front button, but it's quite rusty and hardened, so it can't be hooked onto the front button.
button
Metal buttons are used for this model. It says "RUST PROOF BUTTONS" on the flasher. However, the flasher is rusty after 80 years from manufacture.
outseam
The hems are chain stitched, but they are sewn quite roughly, as was the case with workwear of this era.
fabric
Light ounce denim in 2×1. It's in a non-gluey, non-faded condition, with some noticeable unevenness in the threads that stretch vertically, but the slubby feel to the touch isn't too strong. There are also a few neps in places, but not many. The color is a deep navy with a slight reddish hue, but not black.