Would you be able to give us some information of where your grandmother and her family were from. May be a lead there that can be used. It is not unusual for Danish provinical silversmiths for example to place two, three, or even four makers marks on their work.
Although the first three birds or fowl may not be makers mark, possibly city marks. One of them does not match. The C has not been a useful lead for me with my limited resources. Let's see if other members can take this further.
Hope this helps