Daly's Bartenders' Encyclopedia by Tim Daly (1903, p.122)

2 dashesAngostura bitters — Dr. Siegert's Angostura bittersbase
sherry — good sherry winemodifier
  1. Put the Angostura bitters in a sherry glass.
  2. Fill with good sherry wine and serve.

Daly explicitly frames it as a delightful and exhilarating appetizer.

This is plain fortified-wine service lifted by bitters rather than a mixed cocktail proper.

See also: Sherry Wine Cocktail, Port Wine Cocktail