Although "Master Mason" is the highest degree in the "Free and Accepted Masons" fraternity, there are other appended organizations which require that the member first be a "Master Mason" in order to participate. In each of these appended organizations, the Master Mason is instructed in additional degrees. Some of these appended organizations are; York Rite Mason, Scottish Rite Mason and Shiner.
The "K.S.H.T.W.S.S.T." symbol on a headstone indicates that the person had completed the crytic degrees of the York Rite and was a "Royal Arch Mason" in the York Rite Degrees of Freemasonry.
The headstone of a "Royal Arch Mason" of the York Rite would usually have the Masonic emblem prominently displayed and would also bear the inscription "K S H T W S S T" within a circle on the inside ot the 'keystone' symbol. An example of this is shown below:
The symbol for a 'Master Mason' which is frequently seen on many tombstones is shown below:
Examples of tombstones displaying the Masonic emblem are shown below: