USOC – the “Universal Service Ordering Code” goes way back to AT&T before divestiture. Various vendors shouldn’t have their own codes for the items. Are you asking about USOC numbers for telephone connections such as “RJ-45S, RJ-11C” and such? These codes are examples of those that designate the various types of connections used. There were codes in the old day for everything that was ordered from AT&T. Many are still in use by telephone companies on phone bills. If it is for connectors – check Black Box catalog – they list them with nice diagrams.