Watch List notes:

George III (1760-1820), 'Dorrien Magens' Shilling, 1798, GEORGIVS III DEI GRATIA, no stops except after GRATIA, second laureate and draped bust facing right, rev. . M . B . F. ET . H . REX . F . D . B . ET . L . D . S. R . I . A . T . ET . E., crowned shields cruciform, six strings to Irish harp, with semée of hearts, crown in each angle, edge obliquely milled, 11h (Spink 3747; ESC 2139 [1227] [R5]), rich dark cabinet tone with only a hint of rub to high points, traces of red wax in recesses, otherwise extremely fine, a highly prized numismatic rarity with an exemplary provenance to unquestionably one the greatest cabinets of English coins ever formed, in NGC 'Slaney' holder, graded AU58.
provenance
Slaney, Part I, Spink 163, 15 May 2003, lot 218

For further reading:
T Lismore, 'The Dorrien and Magens Shilling: A Study in Scarcity', The Numismatist (1953), pp. 690-91
Estimate: £25,000 - £30,000