Vintage brown Toni Todd dress - unknown size

Brown dress with pockets, buttons, belt loops but no belt, trim around the collar Zip on the side, snaps at the bust Missing one button Unknown size, but I'm 5'4", 125 lbs, and wear a size 4 to 6 normally. The waist fit me well. My bust size is 34A, and the bust area is large on me. It hits below my knees.