Ancestors of the Finsta family had varying seals.
The knight Erland Israelsson, lawspeaker Birger Persson's uncle, carried a cross between two wings.
His son, the knight Johan Ängel, wore his grandfather's coat of arms, an angel, while Birger took up his mother's coat of arms: two black turned wings with wing brackets outwards on red.
The wings may have been of silver, according to Jan Raneke, a Swedish medieval weapons expert.
His son Jakob Israelsson, who died in 1281, was archbishop of Uppsala, and his grandson Israel Erlandsson was a bishop at Västerås.