You can search for identifiers within the package.
in-package search v0.2.0
letters
letters__.ml
1 2 3 4 (* generated by dune *) (** @canonical Letters.Sendmail_handler *) module Sendmail_handler = Letters__Sendmail_handler
1 2 3 4
(* generated by dune *) (** @canonical Letters.Sendmail_handler *) module Sendmail_handler = Letters__Sendmail_handler