Why do Massachusetts switchboards show both 440 and 450 volts?

Why would circuits on the same South Dakota-class switchboard be labeled 440 volts and 450 volts?

The cause is unresolved. Suggested explanations involve transformer or alternator taps, a winding error, or a deliberate requirement for a higher-voltage circuit.

Drachinifel recalls a photograph of USS Massachusetts with circuits marked 440 volts and 450 volts on the same breaker equipment. The labels challenge a categorical claim that the ship used 440 volts everywhere. The reason for the difference remains unresolved. Possible explanations include the location of the neutral tap in a transformer or alternator, an incorrectly tapped winding, or a deliberate requirement for a slightly higher-voltage circuit. Experience with mistapped modern transformers supplies an analogy, rather than proof of a fault aboard Massachusetts. The 10-volt difference is also judged small relative to a system operating above 400 volts.