In the case of the Wit Stoss altar located in St. Mary's Basilica in Krakow, samples of oak wood were examined, from which the basic structure of the retabulum body, frame profiles, and side formwork of the main cabinet are made.
"The material of all these elements is primary and homogeneous, so it comes from the same area of tree felling. Sequences of growth rings indicate the year 1479 - then the oaks used for the construction of the altar were cut and seasoned. Taking into account the above, it should be assumed that the year 1481 was the year in which the altar cabinet was built in the Basilica," said Prof. Adamowicz.
He recalled that in 1483 Wit Stwosz was exempt from taxes in Krakow, and such a privilege could be obtained when the work at the altar was already well advanced.
Source: Poland Daily 24, naukawpolsce.pap.pl