Sacch. Lact. means Saccharum Lactis which is a fancy way of saying lactose or milk sugar. Lactose has been use for years and continues to be used to make various medications. Lactose is one of the most common excipients used in the practice of pharmacy.
This bottle of Saccharum Lactis is an antique "label under glass" or LUG apothecary bottle. It is a beautiful cobalt blue with gold leafing around the label.