Opinions of the use of these vessels has been divided for years, and a multi-use function would probably seem appropriate. A porringer can best be described as a two handled vessel with or without a cover that was used for drinking or eating.
The word porringer is a derivation of porridge. Other terms for porringer that are encountered are caudle cups or bleeding bowls. Caudle was a type of broth given to women convalescent after childbirth. The other style of porringer that is met with is a low flat vessel with a pierced handle often referred to as a bleeding bowl for use in the bloodletting process. Whilst possibly used for that it was almost certainly used as some sort of feeding vessel perhaps for invalids or for the sick.
Porringers, Bleeding Bowls, or Caudle Cups used from the second quarter of the seventeenth century and reached their height of popularity in the latter part of that century and into the first quarter of the eighteenth. Reproductions of these early styles were also popular in the late Victorian/Edwardian periods.
William Walter has a fine selection of Porringers, Caudle Cups or Bleeding Bowls, whatever you choose to call them!
