1980 AD., Poland, socialist People's Republic, Duke Kazimierz I Odnowiciel commemorative, Warsaw mint, 50 ZÅ‚otych, KM Y 117.

Poland, socialist People's Republic, Duke Kazimierz I Odnowiciel commemorative, engraver: Ewa Olszewska-Borys, Warsaw mint, 1980 AD.,
50 Złotych (ø 30,5 mm / 11,44 g), copper-nickel, 11,70 g. (?) theor. mint weight, mintage 2.503.000 , axis medal alignment ↑↑ (0°), reeded edge,
Obv.: POLSKA RZECZPOSPOLITA LUDOWA / 19 – 80 / {mW} / · ZŁ 50 ZŁ · , eagle dividing date, value below.
Rev.: KAZIMIERZ I ODNOWICIEL 1039-1058 , crowned bust of Kazimierz I Odnowiciel facing.
KM Y 117 ; Parchimowicz 259 ; Schön 1104 .

Year / Mint Mark / Mintage
1980 / MW / 2.503.000
1980 / MW / 5,000 proof

Casimir I the Restorer (Polish: Kazimierz I Odnowiciel; b. Kraków, 25 July 1016 – d. Poznań, 28 November 1058), was Duke of Poland of the Piast dynasty and the de jure monarch of the entire country from 1034 until his death.
He was the only son of Mieszko II Lambert by his wife Richeza, daughter of Count Palatine Ezzo of Lotharingia (of the Ezzonids) and granddaughter of Emperor Otto II.
Casimir is known as the Restorer because he managed to reunite all parts of the Polish Kingdom after a period of turmoil. He reinstated Masovia, Silesia and Pomerania into his realm. However, he failed to crown himself King of Poland, mainly because of internal and external threats to his rule.
More on https://en.wikipedia.org/wiki/Casimir_I_the_Restorer