I am posting this more for mainejman, as to not hijack his magnificent find. This is no where near as old, but is more to show that preservation of bone and ivory is possible. The bone scraper and the ivory Elk bugle teeth were found in a historic indian camp, circa early 1800's. Any bone left on the surface deteriorates, it becomes white and brittle then eventually turns to dust which takes only a few years.All though not in the same condition as the artifact mainejman found it is still remarkable that it survived. The teeth have been drilled and there is also a part of a cloud blower. this is a personal find in central Colorado.
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Your item in the lower, right hand side looks like a bone comb, and an absolutely awesome find. 
And the elk ivories is also an outstanding find. Congratulations!
