From a report by dendrochronologist Ian Tyers, “The Tree-Ring Analysis of Twenty-Three Panel Paintings from the Yale Center for British Art, New Haven,” November 2011
This panel is ca. 477 mm high, ca. 394 mm wide, and ca. 6 mm thick. It is constructed from a single wide vertical oak board, the grain of the board was fast grown and not particularly straight. The board contained sufficient rings for analysis. Sapwood was present on the right edge of this board. The presence of sapwood means that a felling date range can be applied to the panel. The panel had not previously been prepared for tree-ring measurement.
A complete sequence was obtained by a combination of measurements from the upper and lower edges of the board. The sequence was found to match against English reference data.… The tree-ring date obtained from the panel suggests the date of the inscription  is correct.
The board is unusually wide (ca. 3.93–4 mm), this is a surprisingly common feature of English sourced material.