Antique small scale, metal

An antique metal scale, such a special one! If you put a weight on it, the left and right parts will go up on both sides. Where has this been used for? Mail or for something else? Wed love to hear from you. The antique metal scale is in good condition, has some rust spots here and there, see the extra photos. The antique scales are from the 1930s, considering the model and execution.