I saw that exact coin last week on a British archaeological programme called Time Team. Of course the writing around the edge was different, but the image in the centre is of one of the king Henry's. It was a gold coin and thus in perfect condition when found (gold doesn't rust). The detail was stunning.
The "king in a ship" was a pretty common motif for coins in the middle ages. Here's an example:http://coincircuit.com/Closed_Coin_Auction/ViewImage.php?dirname=Closed_Coin_Auction&item=7845903"Great Britain. Noble, ND. S.1799; Fr-112. Henry VI, First Reign, 1422-1461. London mint. Annulet issue (1422-30). Obverse: King in ship holding sword upright, annulet by sword arm. Reverse: Floriated cross with lis at each limb, h in center, crowned lions in angles, annulet in one spandril. Well struck with pleasing surfaces."