Sweet Little Old Amber Bottle

Love this amber bottle, it is a tiny one measuring in at 3.75" x 1.5" x .5" give or take. It is rectangular in shape and has wavy sides. The seams do not go over the top. The bottom say ROUX in block letters, underneath that it says MADE IN U.S.A. Next to Roux there is a 31, possibly the year. That is all I know. I could not find out a clear answer to what Roux was. Thanks for stopping.