I thought I would ride the small wave of medievals started by @echizento

The crown/eagle Krakow half groat (polgrosz) is a signature type for Kingdom of Poland coins from the late 14th through early 16th centuries. A number of CCF members have these in their collections. They were first minted by Wladyslaw Jagiello, who reigned 1386-1434, and were struck by the next 5 kings (at which point these devices were moved to the groat/groschen and continued another century). The earliest
dated royal Polish coin is the 1507 Krakow crown/eagle half groat of Sigismund I.
Early Polish catalogs like Gumowski and Kopicki do not attribute single years to any undated Krakow half groats minted before 1507. But more recent scholarship by Pawlikowski (I have not been able to find this reference; maybe our Polish colleagues know it?) has linked the letters and symbols below the crown on the obverse of Wladyslaw's issues to specific persons associated with the striking of the coins, and has attributed the letter A (Pawlikowski type V = Kop.366) to the date 1403, and the letter n (Pawlikowski type IX = Kopicki 361) to 1407 (Nicolaus for the miner who provided the silver). Other subtypes all have multi-year ranges. I assume these attributions are well accepted in the Polish numismatic community, since they are used by the best known auction houses.
Prices for well struck examples of these two (and some other subtypes of Wladyslaw) seem to be moving upward. I recently won this example of Pawlikowski IX/Kopicki 361 which has a bit of corrosion, but reasonably sharp obverse legend MONE WLADISLAI (note the medieval L which has an exaggerated vertical stroke on the right, making it look more like a modern U ... this has been commented on in some other threads). The reverse with legend REGIS POLONIE (with quite an elaborate letter S) is unfortunately less well struck (or more worn, or both).

