We have some numismatists here - I know a little about Roman coins for instance - but you might get better luck with help over at /r/numismatics/

So the picture is of a polish denar dated from 992-1052 (depends on who you ask) minted under bolesław chrobry (bolesław the brave in english)...the avers is a bird for sure (there's no consensus among numismatists whether it's a peacock, an eagle or a dove...while an eagle might be the most logical conclusion for it's role in polish mythology/heraldry imho it just looks like a peacock) and on the obverse is a stylized byzantine cross...it symbolizes christianity, and since polands baptism was just 30 years prior it was a rather big deal