Where is the serial number located on a Colt 1911?

The 1911 pistol reportedly now has a hidden serial number under the right grip and a micro serial number on the right side. Other steel S&W pistols reportedly have a hidden serial number under the left grip and a micro serial number on the left side.

Do all firearms have serial numbers?

In 1934, Congress enacted the National Firearms Act (NFA). As per the GCA, all firearms manufactured or imported into the United States are required to bear a serial number. This law ―which was effective October 22, 1968― extends the serial requirement beyond the specific group of NFA regulated firearms.