|Yup, AC polarity is correct|
In 1978, when Eolian was built, LED's were an expensive novelty. Therefore the lamps on her control panel that indicate the presence of shore power, generator power, and correct AC polarity were the tried and true neon lamps.
A neon lamp is a stupid simple device - a glass envelope filled with low-pressure neon and containing two closely-spaced metal pins. It will light up when presented with 110V, drawing a vanishingly small current (400 uA). But they don't last forever. Eventually they grow dim and begin to flicker. And then finally they go out.
I had replaced the shore power neon lamp in the power panel in our first year of stewardship of Eolian. It's the one that is lit the most, and therefore was the first to fail. And, coincidentally, it's the only one that is somewhat easy to get at on the inside of the panel.
After 15 years, it had failed again.
But now LEDs are common and cheap. I found these, designed for direct connection to 110V, on the Internet for a couple of bucks apiece. Installing them was not easy. The back side of the power panel is quite crowded, and it was apparent that the original lamps came with the panel and had been installed before any of the wiring.
I did the deed at anchor, with the generator and inverter off, so there was no 110V present to worry about. I got them in, but I had to take an Excedrin afterwards to deal with the cramps in my shoulder.
Hopefully they will last longer than the neon ones.
I'll let you know in 15 years.