My parents owned a 1970 Chevrolet Chevelle and it had seat belts like that. The female end of the buckle was the adjustable side and the male end was longer so that the buckle landed in line with your belly button. The Shoulder belt was similar but its buckle ended at about your chest. To adjust porperly you were supposed to leave a fit width space between your sternum and the belt.
As a kid the crazy part for me was how many seat belts there were in the front seat. SO picture with me...from the passenger door side of the seat...
Male end of the belt (about 18 inches long. They often fell out of the car door and got wet in the rain) Moving towards the center of the car... female buckle for waist belt, female buckle for shoulder belt, female buckle for center belt. Moving towards the drivers side...male end for the center belt, female end for the drivers shoulder belt, female end for the drivers lap belt. And finally, at the drivers door side of the seat, male end of the lap belt.
That is eight things dangling from the seat bight. My dad was kind of OCD about arranging them so that the heavy buckle end hung just off the edge of the seat so they would stay in place.
My dad would only buckle the lap part unless he was on a long trip. Then he would fish the male part of the shoulder buckle from the metal clips on the ceiling and buckle that.
I was born in 1972 and this car lasted long enough for me to drive it. The seats were so old that I had to sit on a pillow to see over the steering wheel and I had to use both feet on the brakes because it did not have power brakes. But boy could it move!!!