El Bar Americano en España by Pedro Chicote (1927, p.67)

0.5 copitagin base
ice — 3 ó 4 pedacitos de hielobase
6 copitaAngostura bitters — Angosturabitter
6 dropsorange bitters — Orange bittersbitter
0.5 copitaDubonet — Source omits the repeated unit and uses dash shorthand.modifier
  1. Agítese muy bien y sírvase en copa de cocktail, con una rodaja de naranja.

Garnish: rodaja de naranja

Ice: Ice

Cocktails by Pedro Chicote (1928, p.209) — Orange slice garnish

0.5 copitagin base
6 dropsorange bitters base
6 dropsAngostura bitters — Angosturabitter
0.5 copitaDubonnet modifier
  1. Shake very well and serve in a cocktail glass with a slice of orange.

Garnish: Orange slice

Ice: 3 to 4 pieces ice

This matters because it preserves a Dubonnet-gin aromatic with both orange bitters and Angostura in the Chicote corpus.

See also: Dubonnet Cocktail, Opera Cocktail