I am not sure the background, but today for Poland, Kingdom of, we have a mixture of overlapping dates for the same currency unit (denar), and one ruling authority, for the currencies before the First Zloty (1526 - 1572):
- Denier (992-1173) - 55 coins
- Denier (1138-1303) - 2 coins
- Denar, continued (1306-1528) - 63 coins
- Wladyslaw Warnenczyk (1434-1444) - 2 coins
In Handbuch der Polnischen Numismatik (1960), Gumowski divides the early Polish coinage roughly like this:
Denar Period (mid-10th c. - 1306)
Grosz/Groschen Period (1306 - 1506).
He explains (p.23) that the introduction of the groschen began in Silesia at the end of the 13th century (following the Bohemian prager groschen), then in Poland in the first half of the 14th century, and finally in Prussia around 1370. He includes the reign of Wladyslaw Lokietek (1306-1333) in the Groschen Period which makes the beginning his reign a reasonable choice for the break between the two currencies. He says initially there were 48 groschen to 1 Polish mark (about 198 g) and initially 12 denars to a groschen, though debasement of the denar would eventually change the ratio to 16:1 and then 18:1.
He does not explicitly say when the Zloty/Gulden is introduced, but mid-way through the reign of Sigismund I (1506-1548) we see larger denominations (3 groschen, 6 grsoschen, thaler) appearing starting from 1528, consistent with the date we have now for the change to zloty.
It would seem the current situation could be cleaned up by keeping two of the currencies while renaming one, as follows:
- Denier or Denar (992-
11731306) Denier (1138-1303)Denar, continuedGrosz or Groschen (1306-1528). Equivalents: 1 grosz = 2 polgrosz = 4 ternars = 12 denarsWladyslaw Warnenczyk (1434-1444)
Probably it is worth mentioning that this is also consistent with key neighbors of Poland. We have our Bohemian currency changing to the groschen at 1300, and we have Lithuania using the groat in the 15th century.
