I took an experimental art course during my undergrad and this exact issue drove me insane. We went though dozens and dozens of examples of experimental/digital/interactive art, and each time the piece would really engaged me up until the point where I read the artists rambling justifications for their work. They just couldn't shut up and let the works stand on their own.
In fact SSCC is simply and unique identifier for particular logistics unit (ie. the one indivisible thing that you send from point A to point B) and does not in any way describe some kind of class of things sharing the same geometry. In the global logistics context GS1 managed SSCC namespace tends to be used only for "large" items (ie. pallets and LTL outsize boxes) while typical package services use either completely proprietary labeling or something that vaguely follows UPU rules for labeling of registered mail. IIRC the Code-128 barcode on FedEx packages contains GS1-128 datastructure that purpotedly encodes SSCC, but I'm not exactly sure that it in fact is correctly formatted SSCC and not just some kind of fedex-proprietary number.
You can buy prefix for your own SSCC codes and then you can form your own serial numbers - based on size or whatever parameter you want.