Final answer:
A cable tester is the tool that could have been used to identify matching ends for each Ethernet cable.
Step-by-step explanation:
The tool that could have been used to identify matching ends for each Ethernet cable is a cable tester. A cable tester can help determine if the cable is terminated correctly and if the wiring inside the cable matches the industry standards. It can show whether the cable has the correct pinout and if the wires are properly connected.