Thank you "buckler" for that information.
As to the size, each arm of the square is 3.75 inches (max dimension), and the distance between the two points is 4.75inches.
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Can anyone tell me what this was used for? Flat backed globular vessel, Limerick (Ireland) silver, circa 1775-1800, George III dynasty. Non-opening lid. Spouts at 45% on either side, opening into vessel.