I would have googled "three horizontal lines" but interesting post nevertheless. From the maths prospective;
" A symbol with three horizontal line segments ( ) resembling the equals sign is used to denote both equality by definition (e.g., means is defined to be equal to ) and congruence (e.g., means 13 divided by 12 leaves a remainder of 1--a fact known to all readers of analog clocks)."
" A symbol with three horizontal line segments ( ) resembling the equals sign is used to denote both equality by definition (e.g., means is defined to be equal to ) and congruence (e.g., means 13 divided by 12 leaves a remainder of 1--a fact known to all readers of analog clocks)."
http://mathworld.wolfram.com/Equal.html