Embossed markings on glass jars, bottles and other containers can add considerably to their monetary value. Embossed markings are important in identifying the vessel's manufacturer, patent, date of production, owner or geographical origin. Depending on the age and condition of the glass jar in question, it can be difficult to make out what, exactly, an embossed marking represents. Take steps to identify the embossed markings to accurately determine the value of your glass jar.
Use different kinds of lighting to determine the jar's embossed markings. Try examining the embossed marking in low light and in bright light. Carefully insert a lit flashlight inside the jar to back-light the embossed marking. Examine the embossed marking outside in broad daylight, in the early morning and at dusk to see if the markings are made more legible in any of these conditions.
Change the color behind the embossed marking using pieces of construction paper in various colors. Curve the piece of construction paper so that it fits neatly inside the jar and position it behind the embossed marking. Try different colors of construction paper to see if any particular color makes the embossed marking easier to read. Keep in mind that this is a more effective method with light-colored or translucent glass.
Take a picture of the embossed marking on your jar using a flash. The camera's flash may help define the embossed marking, making it easier to read from a photograph. Zoom in as close as you can to the embossed marking without losing focus, and make sure the flash on your camera is charged. Use a digital SLR camera if you have one, although any high-quality digital camera will also work. Avoid mobile phone cameras, which have lower resolution lenses and produce photographs with highly variable quality.
Consult a guide book that identifies different types of collectable glass jars. Bill Schroeder's 1980 book, "1000 Fruit Jars," is an authoritative work that identifies hundreds of types of glass collector's items, highlighting their embossed markings and glass color as identifying characteristics.
Bring your jar to an expert, antique dealer or auctioneer for a professional identification and appraisal. For a fee, an expert can use her expertise and familiarity with glass collectors' items to accurately identify your glass jar and tell you what the embossed marking represents and the time period of its manufacture. You can also acquire a written certificate from the expert should you need to prove your glass jar's authenticity when you decide to sell or show it.