15   Time for instituting proceedings for offence

Proceedings for an offence under the Principal Act or this Act may be instituted at any time before:

(a)  the expiration of the period of 3 years that next succeeds the commission of the offence, and

(b)  in the case of an offence under section 28 (1) (Requirements as to packaging of pre-packed articles) or 32 (1) (a) (Offence of packing short measure) of the Principal Act, the expiration of the period referred to in paragraph (a) or the expiration of the period of 1 year that next succeeds the discovery by an inspector of the commission of the offence, whichever is the later.