Google dictionary has this information about the origin of ex: Does ex have a full form? Is short for exempli gratia, and is in common use to introduce an example within a sentence.
But what is the origin of the usage as a prefix in the words. Submit a sample of academic writing, e.g., a dissertation chapter. 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.