Import marks are not normally placed on stocks as they can be changed to easily. That is why they stamped the barrels and now the receivers with the import makings. Stocks that were used over seas that never went through a rebuild would of course not be stamped. Stocks that were replaced at a unit level anywhere would not have a rebuild stamp on it too. Some CMPicon carbines and stocks from Greece had not markings on them while most of the carbines and stocks from Italyicon has the famous FAT stamp on them. The number 3 could have come from just about anywhere or time. But it does look a bit more like a rack number as Jim said.