https://en.m.wikipedia.org/wiki/Holy_Royal_Arch

By adding a further explanation to the practical lessons of Craft Freemasonry, the Royal Arch is seen as an extension of the preceding degrees and the philosophical lessons conveyed are appropriate to that stage in a candidate's Masonic development. The symbol or Grand Emblem of Royal Arch Masonry is the Triple Tau.

https://en.m.wikipedia.org/wiki/Tau

Tau was derived from the Phoenician letter taw Phoenician taw.svg (𐤕). Letters that arose from tau include Roman T and Cyrillic Te (Т, т).

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Keystone Arch

Holy Royal Arch

Nature King Arch

YDNA Source Heirarchy

All symbolism translation

Another X/T in control triangle/circle

+O𐤈Q+