Vintage Native American Sterling Silver Thunderbird Pendant

Sterling silver Thunderbird pendant is unmarked and tests as at least 925.  It measures 1 5/8 Inches by 3/4 inch wide and it weighs 3.4 grams.  It appears someone put some kind of lacquer on the back which is chipping off at the edges.  I gave a mild attempt to remove it with acetone but it did not work.