Are you referring to the blue backs missing the set number? Topsun cards don’t have a “stamp” as you say. More info is needed.
@aminal They’re not from the Topsun printing. Looks like a kid was testing out his or her stamp toy. Either that or… sometimes parents mark toys so there won’t be bickering among the children over who owns which toy… A common problem 
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Thanks jkanly! Had so many of them i thought something was fishy. Glad to have it explained.
