***Son says the symbol on that post is called a “triskele” and is a Nazi symbol ...
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(snip)The triskele (or triskelion) is an ancient symbol originating in pre-Christian Europe. The symbol consists of three curved or jointed segments spiraling from a common center. One version of the triskele, with three human legs, has been used in the coat of arms for the Isle of Man and the Kingdom of Naples. An abstracted triskele appears on the seal of the United States Department of Transportation.
Because of the AWB usage, it is this “three sevens” version of the triskele that is most commonly associated with white supremacy. It is a common type of white supremacist tattoo and appears in places such as the logo for the racist skinhead group Blood & Honour.
White supremacists do use other variations of the triskele, too, such as curved triskeles, but so do a much larger number of non-extremists. As a result, such triskeles must be judged very carefully in their context to avoid mistaken assumptions.
https://www.adl.org/education/references/hate-symbols/triskele
It sounds similar to the “White Power” hand sign that folks were throwing a fuss over (also known as the A-OK sign).
Otherwise, Star Trek (The Gamesters of Triskelion - look at the floor of the arena), the Department of Transportation (logo), and Boeing (the Triple Seven), among others can all be considered as Nazis.
As stated above “...such triskeles must be judged very carefully in their context to avoid mistaken assumptions..”