Please add this character used in Old Polish: $A7C0 and $A7C1. This letter is obtained by the letter o combined with the tails at the top and bottom.
This image containing the modern and old Polish orthography alphabets, using the modern alphabet used by Libor Sztemon in his alphabets, diacritics and phonetics page may be helpful.
Notes: 1) Diphthongs are shown in gray.