i have a charcoal painting on board. signed ingwersen in penil?

[Betty]

i have a charcoal painting done on board. its signed ingwersen in pencil. on the back of the board i a o. what does this mean? at the bottom it says it has a copy wright sign. then it says 1979 arthur a. kaplan co.n.y.c. h- 4532. published for edward art prod. litho in usa. could you please tell me what the o on back means? and if this is worth any money. thank you and god bless.