XHTF CHAMPION AGATE NOT ALLEY ! MILK WHITE SOLID BASE SWIRL .58" NM+/- MDD167

you can see the different examples on buymarblesdotcome between the alleys and champions ... basically the alleys base are lighter type of off white and the champions are more like a china dish white or milk white as they made chinese checkers marbles and this was the change from game marbles to toy marbles with the same base white ... the difference is hundreds of dollars ... you will not find this one on ebay or by many collectors ...  XHTF CHAMPION AGATE NOT ALLEY ! MILK WHITE SOLID BASE SWIRL .58"  NM+/- MDD167
PRE-1970S SWIRLS
Swirl marbles were part of Champion's regular run from 1938 up into the early to middle 1970s. Most of these appear to have been opaque white-based. On these marbles there is usually only one color in addition to the white, with swirl patterns forming ribbons that fill little of the base glass, as opposed to the swirls by 
 
many other companies that cover the majority of the white.
POST 1970
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As mentioned, sometime during the first half of the 1970s Champ