I have been thinking the same as fancypants as there is also no wear to this object. If utilitarian in use, such as a calendar or counter, it would be handled and the etchings would be smooth from use. In no way do I think it is from the pre-1900s. I was originally thinking Africa and the 1950s but could not find anything that looked like the centipede-like figures. I only put the Mayan centipedes out there because they were the closest I could find. I do not think it is from the Mayan times. I also think the horn is not that old and not rhino horn. I was thinking more buffalo or carved down water buffalo but I am not familiar with African dark-horned animals that much.
An interesting comment that it looks like part of a musical instrument. Bell part from a snake dancer's flute?
As to the smallness of the etchings...that has been done many, many times before by the naked eye with miniature books, miniature carvings, etc. Not unusual in the least.