Watch List notes:

William III (1694-1702), Exeter Halfcrown, 1697 NONO, inverted A for second V in GVLIELMVS, first laureate, draped and cuirassed bust right, E below, rev. crowned shields cruciform, large shields, ordinary harp with seven strings, lettered edge, upside down A for V in TVTAMEN, 14.34g, 6h (cf. Bull 1075 [R5]; ESC 547A; Spink 3490), flecking and adjustment marks both sides and cleaned, the A for V on the obverse nevertheless remarkably clear, struck details almost very fine, very rare.
Bull 1075 notes the edge 'error' (which is probably only a die flaw), and considers it worthy of R5, but does not know of the A for V on the obverse, presumably meaning this is rarer still.
Estimate: £200.00 - £300.00