It may have been obvious to you that it was diamond core drills used by the US gov. in 1892 but it was not to me. I kept thinking that using diamonds would have prohibitively expensive for this kind of use. Now I see at $6 or $7 a carat 1871 prices that it makes total sense. I also wanted to add that the description that was used, "annular pointed diamond" was clearly not referring to sharpened to a diamond point steel drills, which is also something you discussed. I will try to keep up in the future.