Ok, this photo is not a tombstone. The gravestone photos are below and should be a strong example of what not to do when restoring grave markers. The stones are in a local cemetery and obviously repaired by someone with good intentions but no clue. The above stone was photographed in April 2016 and the lower photo was taken three days ago. It was simply a matter of time before the upper part of the stone broke away from the lower. The extreme angle that the stone was leaning also did not help the repair's cause.
The proper method would have been to level the lower stone, clean both pieces with D2, bond the stones together with an epoxy such as Akemi 2030, clamp and hold the stones in position for 24 hours, and then fill the seam/joint with a Lithomex mortar.