Figure 1.--This German boy, probably in the 1910s is taking no chances. He wears both a belt and suspenders. They are the button type of suspsanders. Botice how they attach to the inside of hids waistband.

There were two basic types of suspenders which related to how they were attached to the pants. EThere were variants, but these were the two basic types. Early suspenders were done with button attachments. Most of the suspenders we see in the 19th and early 20th century are the button type. I'm not sure when metal clasps first appeared, perhaps the early 20th century. We note quite a few men and many boys wearing clip-on suspenders during the 1930s. The 1939 Sears Garter Waist ad shows ONLY clip-on suspenders for boys. The clip-on style was obviously invented earlier than this. Clip-on suspenders seem to have been originally an American invention, but they were widely worn in Europe after World War II. As a boy in the 40s, I only recall seeing the metal clips. Many boys used to prefer metal clips to buttons because of the ease of attachment and detachment, although clips tend to be more damaging to trousers than buttons because of the teeth required to hold them tightly in place.