Vintage marbles were beautifully made, with swirls of colours inside thick glass. They are superior to today's play marbles; the colourings and patterns inside the marbles resembled the blown art glass of the time with a deeper incision of colours. Vintage glass marbles are highly collectable, especially when they are in good condition. Old marbles include German-made Benningtons, and American companies made marbles up until the 1940s. After 1950, foreign marble-makers put most American marble companies out of business.
Examine the marbles for scratches or pits, using a loupe magnifying glass. These small magnifying glasses are used by professional dealers of antiquities to examine markings. Hold the loupe up close to a clear surface of the marble, and look inside for internal cracks. Cracked interior and exterior vintage marbles will be worth considerably less than those in mint condition.
Value old marbles by size. Very large marbles are worth more than average-sized marbles. Look for small marbles as well. The odder the size on vintage marbles, the more the marbles may be worth, especially if they have the striking colours and intricate inner design work.
Look for marbles that have swirl designs inside. Swirls look almost like the pattern on a candy cane, yet with circular, or tubular centres within the marble. Keep an eye out for translucent vintage marbles with an interior swirl design. Translucent marbles will appear clear or have the appearance of lead glass -- not entirely see-through, but clear to the centre.
Check to see if the marble was machine-made or handmade. Machine-made marbles are more colourful, and creatively infused with colour. Handmade marbles will have the inner parts of the marble more defined, with tubes or swirl designs.
Count how many colours are on the machine-made marbles. The more colours, the more valuable the marble, especially when there are more than three colours. Look for dark blues and reds. Dark blue marbles with the swirl interior, or machine-made made marbles that are infused with colour can be quite valuable.
Don't pass up marbles that have figures inside, such as numerals or animals. Even if these marbles are lacking a swirl design or colours, the character marbles are quite collectable and easier to identify when valuing.
Go to the local library and look in research books on marbles to identify your particular type of marble and to get an accurate value. Take the marble or marbles to an expert dealer who is experienced with evaluating vintage marbles, and inquire about getting an appraisal. Compare old marbles to new ones. New marbles are inferior to the old. The glass is not as thick and may appear cloudy. The colour and design within new marbles are not art-glass quality, as on the vintage.