This stone was discovered at the southwestern corner of the Temple Mount. Evidently it had been the upper course of the southwestern corner, and from this position a priest would have blown a trumpet to announce the beginning and end of the sabbath and festivals.
Note the indentation on the stone where the priest probably had stood.
It probably fell from its original position at the top of the corner to the street level below at the time when the Romans destroyed Jerusalem in A.D. 70.
For a detail of the inscription click here.