It shall be presumed, for the purposes of this part, that all beer and wine imported into this State by a beer manufacturer or wine grower or importer has been sold in this State at the time it is received by the licensee, unless it is proved to the satisfaction of the board, on forms prescribed by the board, that the beer or wine is still in the possession of the beer manufacturer or the wine grower in internal revenue bond within this State, or has been exported from this State by the licensee making the report or has been sold by him for export and actually exported from this State, or is otherwise exempt under this part.