Also from his site (which does contain his stock):
1952, dies 3+C, BMC-; F.-; S.4117 (Unique), this coin , carbon spot by second N of PENNY and another behind head, otherwise brilliant, and the only known example,
Ex. A H Baldwin 125th Centennary Auction, 13th October 1997 and Rasmussen List 9 (C109). Up until its appearance in the Baldwin sale the existence of this piece was not known to the collecting fraternity, with the exception of Baldwin's management. It now joins the ranks along with the other great rarities, the pennies of 1933, 1937 (Edward VIII) and the 1954.