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Google dictionary has this information about the origin of ex: 防爆标志ex d iic t6 gb是一个详细的电气设备防爆标识，它由多个部分组成。 ex是中国及国际电工委员会的防爆标志，表示该设备遵循gb3836和iec60079的防爆标准。 d代. Does ex have a full form?
Officials scour mountainous area of Montana for exUS soldier suspected
But what is the origin of the usage as a prefix in the words.
