Denars were issued in many variations over the next few centuries by successive rulers of Poland.   Denars were actually fractions of a base unit of silver, known as a GRZYWNA.  A Grzywna varied over time but was between 182.5 and 197.68 grams of silver during this period of time.  Usually there were 240 denars to a Grzywna, and sometimes there were 265.  Over the years, the purity of the silver went down.  By adding lower value metals to the silver alloy, more coins could be made from a given amount of silver.  This policy, known as debasing, occurred to various degrees over the centuries.

Another coin that made it's appearance early in Poland's history was the BRAKTEAT, a very small and very thin coin that had an image on one side only.  These coins often had merely a symbol on them such as a cross, an animal, a crude face or a hand to name just a few.  Brakteats were issued by Kings, Princes, the Church and others, and remained in use for a few hundred years.
Some Brakteats were known as "Guziczkowe" as they resembled buttons (concave on one side, convex on the other).

Copies of Byzantine type coins were used in Poland during the 12th and 13th centuries.
Coins of other Kingdoms, such as those of Hungary and Bohemia were also used in Poland.
German migrants also brought coins into Poland.  Since Roman times, Poles have been trading amber, which was found on the Baltic coast.  Many trade routes passed through Poland over the centuries.  The traders brought with them many "foreign" coins.

Kazimierz the Great brought about significant change in the monetary system by introducing the GROSZ.
1 Denar = a Half Grosz. (POLGROSZE)
2 Denars = 1 Grosz.
There were 48 Groszy (or 96 Denars) to a Grzywna (197 grams of silver).
The Grosz and Half Grosz as well as Denars were issued by many subsequent Polish Rulers.
Usually there was a Crown on one side and a Polish Eagle on the other, but the Bohemian Lion, Royal Monogram or coat of Arms was sometimes used.  In some cases, Religious figures like the Madonna were used.  Kazimierz  had no direct heir and under much protest the Polish throne passed to his nephew Ludwik Wegierski (Louis the Great of Hungary).  Some Hungarian coins of Ludwik have Polish titles in their legends.

Ludwik died in 1382 having only 3 daughters as his heirs.  After a brief period of struggle, his middle daughter Hedwig (Jadwiga), was chosen as "King" of Poland in 1384.  She remained "King" until 1386 when she married Wladyslaw Jagiello the Grand Duke of Lithuania.  She then became Queen of Poland.  This marriage unified the Polish and Lithuanian kingdoms.  Eventually this brought about new coins for use in Lithuania based on the Denar and the Half Grosz but with the Lithuanian Coat of Arms or POGON in place of the Polish Eagle on some coins.  Under Jagiello, Poland defeated the Teutonic Knights who were trying to expand southward from the Baltic sea (Prussia).  Later, a small thin silver coin known as SZELAG started to be used in these Northern areas (becoming a copper Shilling much later).   Although the Jagiellon Dynasty ruled Poland until 1572, .the title of MAGNUS DUX LITVA (Grand Duke of Lithuania, often abbreviated MDL) appeared on most coins of subsequent Polish Kings, including the last Polish King Stanislaw August Poniatowski in 1795.

During the Jagiellonian period, coins were issued for Gdansk, Torun, Elblag, and other areas under Polish rule.  Under the Reign of Zygmunt I Stary, several new coin types were produced.  They were based on the ZLOTY system introduced in 1526.  Some credit for these monetary reforms belongs to Kopernicus, who was as much an Economist as he was an Astronomer.
1 Zloty = 30 groszy.
1 Grosz = 3 Szelags
1 Szelag = 6 Denars
The Grosz came in many multiples.  POLGROSZE = a half Grosz, a TROJAK was 3 Grosz
and a SZOSTAK was 6 Grosz.  The silver TALAR was also introduced under Zygmunt II August in 1564.  It was meant to equal a GOLD DUKAT.  The value of the Talar was 90 Grosz.  Another coin emerged as the ORT which was 18 Grosz or 1/5 of a Talar (originally 1/4 Talar).

Half Gros of Jan I Albrecht 1492-1501

Half Gros of Zygmunt II August, 1559.
 
The Jagiellon Dynasty ended in 1572 with the death of Zygmunt II August.  The Polish Throne was passed to elected foreigners.  Henryk Walezy (Henri de Valoris of France) was the first of these Kings (1573-1574), but resigned shortly after to take the French throne.  Some coins of Henryk minted in France name him as "King of France and Poland" long after his abdication to the Polish throne.

Stefan Batory ( a Transylvanian) became King in 1574 and ruled until 1586.  Batory defeated the then Russian Tsar Ivan IV (the Terrible) on three separate occasions.  Most of the previous denominations of coinage remained in use.  Coins also began to be issued from Riga.

Gros of Stefan Batory, Riga, 1584

After Batory's un-expected death, Zygmunt III Wasa, a Swede, became King of Poland.  He ruled until 1632 and a vast number of coins were struck under his rule.  There are of 500 different coin variations struck under this King from several different mints.
For information about old Polish coins struck in Riga, Latvia, click here

1620 Zygmunt III Wasa 3 half-gros, known as POLTORAKI or DREIPOLCHER

1621 ORT (18 Groszy or 1/5 of a Talar) of Zygmunt III Wasa.

 
Jan Kazimierz became King in 1649 and ruled until he abdicated in 1668.  Many low value coins were struck during his reign, especially copper Szelags.  Silver coins were also produced that had a lower percentage of pure silver in them (debased).
 
Under the Wettin Dynasty (August II and August III) coins minted in other Kingdoms, such as Saxony, contained references to Polish Royal titles.  Although not really Polish coins, they can be an interesting addition to a Polish collection.

Saxony 1/3 Talar 1767,  XAVIERVS DG REG PR POL & LITH DUX SAX.
(XAVIERVS DEI GRATIA REGIUS PRINCEPS POLONIAE ET LITHUANIE)
The titles and a Coat of Arms were Passed down from August III to his heirs in Saxony.

Major changes in coinage occurred under Poland's last King, Stanislaw August Poniatowski.
This king oversaw the partition of Poland among Austria, Russia and Prussia.
He also established the Warsaw mint.
Click here to go to the Warsaw mint's site on the history of the mint.

In 1766 the Kolognian Grzywna of 233.8 grams of silver was used as the base unit.
This was equal to 10 silver Talars.
1 Talar = 8 Zloty
A Gold Dukat now equaled 16 3/4 Zloty.
After 1786 the system was changed to 83.5 Zloty to a Grzywna and a Dukat now had 18 Zloty.
In 1794, a popular uprising led by Tadeusz Koszciuszko led to some Treasury notes being issued.  Click here for more info

Coins of the Russian Occupation (the so-called Kingdom of Poland or Krolestwo Polskie) starting in 1815 are identifiable by the presence of a Russian 2-headed Eagle.  They have Polish legends and denominations (groszy or zloty).  The portrait of the Russian Tsar appears on some denominations.  Tsar Alexander also has the title Krol Polskie (King of Poland), even though he was not the legitimate King of Poland.

2 zlote, 1820.

These coins were discontinued after several uprisings against the Russians.  During an 1830 uprising,  some coins and paper notes were issued by the Polish "rebels".  After 1830, the coins were replaced with Russo-Polish coins, most of which had both Polish and Russian writing on them (also both Zloty or Groszy/Rouble or Kopek denominations).  Some of the coins had Polish only, but still had the 2-headed Russian Romanov Eagle on it.   Starting in 1850, Russian coinage began to replace the coins in Poland in order to remove any reminders that Poland was separate from Russia.  Coins were still made at the Warsaw mint, and had the MW mint mark.   This mark appears as "BM" (Cyrillic for VM) on Russian coins minted at Warsaw.

Coins Through the Ages, Laurence BROWN, Bonanza Books, New York 1961

Warsaw mint's history http://www.mennica.com.pl/english/gab_num/1764_1787.html

Page on the history of the Polish monetary system http://www.bakk.com/BlazeK/monetary.htm