on which it becomes a prescription medicine, restricted medicine, or pharmacy-only medicine (as the case may be) if, at that date, the medicine was part of the existing stock-in-trade in New Zealand of the retailer. (6) For the purposes of subclauses (4) and (5), any goods purchased before the date on which a substance becomes a prescription medicine, restricted medicine, or pharmacy-only medicine (as the case may be) for importation into New Zealand are deemed to be part of the purchaser's stock-in-trade in New Zealand. (7) In any proceedings for an offence against section 44 of the Act in respect of any container that does not comply with regulation 13(1)(f), (g), or (h) , the onus is on the defendant to prove that the relevant paragraph does not apply by virtue of subclause (4) or (5) of this regulation. 17 Form and manner of labelling (1) Subject to subclause (4), every label that is required by these regulations to be borne on a container shall --  (a) be conspicuously written in English and, for each statement separately required, be in a colour or colours contrasting strongly with the statement's background; and (b) be legibly and durably marked either on the material of the container or on material firmly and securely attached to the container; and (c) be of such nature and material that it will not fade to the extent of becoming illegible, or become detached, by the influence of --  (i) light; or (ii) atmospheric humidity or dryness; or