If you can post a pic of the painting and the signature it would help !! As a rule professional artists would not initial the last name !! Name recognition is how an artist makes his living !! How would any one know who this person is with only an M. in the signature !! Most likely your painting was done by a hobby artist !! Not one who intends to sell his/her work !! Hobby artists are not listed !! You have to have a sales record for that !!