Hi Simon,
Just giving a shout out to Hugo Ensslin (1917) where Craddock got a lot of his recipes. Ensslin's is identical apart from the Angostura. He used Peychaud;s - suits it really well with spicy fruit.

Merry Widow Cocktail Hugo Ensslin 1917
1/2 Sry Gin
1/2 French Vermouth
2 dashes Benedictine
1 dash Peychaud Bitters
2 dashes Absinthe