Nearly all US ordnance/weapons were subcontracted out to various companies from WWII through the Vietnam War. For example Singer Sewing Machine made some firearms; Ithaca manufactured some Colt .45...
Those devices have existed since gunpowder has existed; at least since the 1100's. They were COMMONLY used during the Napoleonic era, by fighting men known as "Grenadiers."
The Pineapple Grednades of World War 2 were made of tin/metal and filled with an explosive powder. The modern grenades are different. They look different and have different chemicals inside them.
Depends on which grenade. Assuming you mean the standard fragmentation grenade used by the US military, they are made from sheet steel. Coiled inside of the body is a steel spring, notched in over...