Macaw Bird Print

I bought a picture with a print of 2 macaws from an estate sale in 1982. I just loved the picture and never thought about who made it or what it could be worth. Now I would love any information about it. It is 18x12 and the frame looks to be old. For it has nails holding it together.Someone had tore off the flimsy fragile paper before the estate sale. This exposed what looks like older cardboard type paper. It has nails holding it in place. The print has a signature in the lower right corner. It looks like it could be 2 names one under the other. Since the frame is covering most of the name I can only see a ST. I'm not sure if I should remove the nails to see the entire name. I would appreciate any help. Thank you

Thank you designKing for helping me identify it. I paid maybe $10.00 for it and didn't notice that the back paper was peeled off until after the auction. The print just made me feel happy and I still enjoy it. Thank you again for your help. I'm including a photo of the side showing the nails and cardboard. I trying to resist removing the nails so I can read the name.