Marbles have been valued by collectors for nearly 100 years. Collectors must quickly identify a vintage marble, recognise its manufacturer, spot any flaws and have an in-depth knowledge of the market. Value is only assigned by what another collector pays for a particular piece. Avid collectors regularly study realised prices at vintage marble auctions to maintain a working knowledge of a particular piece's worth.
Identify Champion Agate marbles by their trademark swirls. These marbles are often difficult to distinguish from swirled marbles made by other manufacturers. Look for recognisable patterns such as the "Furnace Swirl" and the "Champion Swirl."
Look for a corkscrew pattern when identifying marbles manufactured by Akro Agate. Corkscrew patterns generally have a white base, with a second colour twisted into a helix. Other styles and patterns include Moonies, oxbloods and corkscrews with three or more colours.
Examine the marble for a logo from a comic strip. These specially licensed marbles were typically manufactured by the Peltier Glass Company, and are prized by collectors. More common marbles made by this company are from their colourful "National Line Rainbo" collection. The various patterns found in this series are usually nicknamed by collectors; various patterns are given names such as a "Zebra" or "Flaming Dragon."
Recognise valuable "Guinea" marbles from the Christensen Agate Company by their brilliant, rare colours and specific pattern. The "Guinea" pattern is a tiger-stripe featuring three or more colours. It is one of the most prized vintage marbles on the collector market.
Identify marbles manufactured before 1950 -- by the Vitro Agate Company -- by their patchwork of colours. Patches-style marbles are generally opaque; they feature three to four colours in a rough, quilt-like pattern.
Inspect the marble using a jeweller's loupe. Check for pits, cracks, chips or other damage. Evidence of wear or damage reduces the realised price of a marble at auction by over 50 per cent.
Check the marble for overall shine. A marble dulled through use or handling has significantly less valuable than one with a bright, glossy finish.
Look for fine bubbles and inclusions; these are signs of a flawed marble or a possible fake. Mass produced and imported cat-eye marbles often have tiny bubbles in the glass; these flaws are evident when viewed through a jeweller's loupe.
Evaluate the marble for its artistic merit. This is a very subjective measurement, because particular qualities of a marble are valued differently by individual collectors. The qualities in most demand are bright, four-color combinations, recognisable shapes within clear glass and marbles that are unusually large or small.
Review auction results and locate marbles with similar qualities. A comparable marble is one of similar size, colour and quality, made by the same manufacturer. Marbles typically sell for 50 to 75 per cent of the realised auction value when offered in a private sale. Commissions and fees charged by the auction house are responsible for the lowered price.