To answer your question ---- NO, the grave marker for John O'Brien has not been placed in the cemetery. It was ordered from the government in 2007 and has been received by the local Funeral home - in 2008 - where it sits waiting to be placed in the Shackelford Cemetery where John was buried in 1875 - and where there are 7 members of his family buried.
A scan of his marker is on my Family Tree Maker website.
After some discussion and debate, it was decided to order the metal FLAT marker since the nice folks in Missouri use those long scythe type mowers and the upright markers seem to get in their way. Many of the original markers are either knocked down, run over and buried or they were broken when being mowed down, thrown against the fence line and have since disappeared.