Evaluation of Wiring Gauge and Code Compliance

What happens here

While observing the internal wiring of the disconnect, the electrician notes that the power feed appears to be either #8 or #10 gauge wire. He discusses with his son whether #10 wire is sufficient for a 60 Amp, 3-phase circuit. He clarifies that a lower size power feed, like #10 wire, can be acceptable as long as the disconnect itself is appropriately rated, and the actual current draw does not exceed the power rating (60 Amps). He also mentions that, depending on the new equipment's specifications, a 30 Amp disconnect might have been used instead.

Goal: Determine the adequacy of existing wiring for the disconnect's rating