Coneflower, water-based ink on Fabriano paper, image: 6 x 4 inches, paper: 8 x 6 inches
B.A.T. in the lower left stands for bon à tirer.
From the Dictionary of Printmaking Terms:
"Once a printed image meets the artist's expectations, this becomes a bon à tirer ("good to pull") proof. This proof is often signed by the artist to indicate his approval and is used for comparison purposes by the printer."