Depression glass was first produced in the late 1920s and was marketed to the average housewife. The glass was mass produced on machines and available for a few cents per piece, making it affordable for the average family coming out of the Depression of the 1930s. Authentic depression glass comes in many colors and raised patterns. Reproductions of depression glass have made it difficult to distinguish whether a piece is authentic. Know the signs of authentic depression glass before you make a purchase.
Inspect the piece of glassware for raised seams along the sides of the glassware. Raised seams were common during the manufacturing process for depression glass. Most reproduction depression glass does not have seams.
Examine the glass for wavy "straw-mark" ripples that appear on the bottom of some authentic depression glass. These marks were formed when the glass molds aged. Reproduction glass will not carry these imperfections.
Examine smooth portions of the glass for scratches. Authentic depression glass scratched easily with daily use and from silverware marks.
Compare the glass pattern and color with a reputable depression glass book, such as "Pocket Guide to Depression Glass & More (16th Edition)" by Gene and Cathy Florence. Many reproduction pieces will not be an exact match of the authentic piece. Specifically examine the color shade and the raised pattern. Depressionglasssecrets.com has a free e-book available that will also help identify authentic depression glass. (See link in References.)
Check online listings carefully before you buy. Look for a complete description from the seller including the condition, color, pattern and maker of the glass. A vague listing should be a red flag that the seller does not have authentic depression glass. If the piece is worth pursuing, send a query to the seller for additional details. Look carefully at the seller's feedback. Previous buyers will flag the seller for reproduction glass being sold as authentic.