Art Nouveau TOC incised and painted panel, and detail of Incised, Stylized Initials

This  is a mysterious and wonderful art object from the Art Nouveau era of over 100 years ago. The subject is plain to see, done with incised lines on a built-up panel of about 18" X 36". The discoloration and worm holes are evidence of many decades of neglect in a damp basement. Here it is, retrieved, wondered about, and still not sure who did it and what to do with it. It has a damp, rotten smell to it, so I keep it wrapped in foil.

Click on the images for a full-screen view.

Any idea who the artist is? I see an A and a B, maybe two Bs.