18th Century Painting of "Master Simpson" by A.W Devis

I recently picked up what looks to be a very old painting of "Master Simpson" by the famous Masters A.W. Devis. I know this isnt an original painting but what i am interested in is finding out exactly what it may be and how much it may be worth.

For started based on the condition and the aging of the board it is on and the frame it in it does look to be very old. From my research i believe it could possibly be either a very old reproduction and/or a Transfer painting onto a board. If it is a transfer i am not sure if it was a transfer from another painting or from a print of the original.

I have provided close up pic to help and a close up pic of the edge of the board to try an show that it does indeed look very old.