"Wert on back of" is not a phrase or word with a clear definition or meaning. Therefore, it is difficult to provide antonyms or opposites for this term. However, if we take "wert" to mean "were," the antonyms could be "weren't" or "wasn't." Additionally, if we consider "back of" as a prepositional phrase denoting a location, the antonym would be "front of." In general, antonyms are words that have opposite meanings, such as hot and cold, up and down or fast and slow. However, in the case of "wert on back of," there is no clear context to determine suitable antonyms.