From your edge shot it looks like it is attached to the board backing, not painted on. Could be a sepia print. It looks like it was reframed as the artist would have had his name completely within the picture and not on the border I think. I would see if you can lift a corner of it from the backing board. Of course we cannot see the picture like you can but you should be able to tell if its just a print that, over the years, has stuck to the board.