Congratulations on your first ancient coin purchase! I wouldn’t be too bothered by the pin-like object which appears to be just a stray silver globule adhering to the
tetradrachm from the minting process creating the optical illusion of an anachronistic metal pin.
NGC are very professional at encapsulating, conserving and
grading ancient coins. They would never stoop to damaging irregularly-shaped
ancient coins by anchoring them in place with metal pins or anything like that.
My very first ancient coin purchase was also the iconic and chunky Athenian
Owl. They were the first widely-used international coins of the ancient world. People were excited by the explosion of new Western civilization and the prosperity of
Athens - the coin itself came to represent those riches. The widespread exchange of the Owls helped to spread Greek culture throughout the Mediterranean. It’s believed that the U.S. President Teddy Roosevelt carried an Athenian
Owl as a lucky charm, one that influenced him to redesign American coins.
Athens, Attica, Greece (c.454-404 BC), Old Style Silver Tetradrachm, SNG Cop 31, SNG München 49, Kroll 8, Dewing 1611, Gulbenkian 519, HGC 4 1597, SGCV I 2526, EF, well-centred and struck on a tight flan, bold high relief, lightly toned, minor marks, reverse some hoard encrustations, small edge cracks, weight 17.25g, maximum diameter 23.0mm, die axis 330°, Athens mint, c.454-404 BC; obverse head of Athena right, almond shaped eye, crested helmet with olive leaves and floral scroll, wire necklace, round earring, hair in parallel curves; reverse owl standing right, head facing, erect in posture, olive sprig and crescent left, AΘE downward on right, all within incuse square.