From the link below
OXEN/STEER BRASS HORN KNOBS TIP GUARDS
These little hollow brass ball things are called ox knobs. In Nova Scotia we most often see them used on the tips of horns of oxen but they are also used on steer. The end of the horn is like your fingernail - no nerves - so it is carefully pared with a knife to fit the inside of the brass knob - some are threaded and some smooth. The know is twisted on - some apply a glue or epoxy. The knobs add a nice decorative touch to a team of oxen and some believe they help prevent accidental puncture incidents animal to animal or ox to human. This group has five different versioins. Three are threaded and the largest one is smooth inside. Each has a hole drilled in the side so you can add a pin to help keep the knob on the horn.
These little hollow brass ball things are called ox knobs. In Nova Scotia we most often see them used on the tips of horns of oxen but they are also used on steer. The end of the horn is like your fin
www.worthpoint.com
Others from the same site:
View attachment 15211
oxen horn knob in the WorthPoint Worthopedia® Price Guide, page 1 of 3
www.worthpoint.com