This looks like a regular wrench but it appears to be very old and rusty. It has what appears to be "F163", if that means anything to anyone. The opening on the large end is about 1 3/8 inches; the smaller opening is about 7/8 inches. It appears that the wrench had a flat extension on one side of the large opening, but it has been broken off. This wrench has been in my tool box forever but I have no idea where I got it or when.