"Gould 0738" wrote
Just like an analog clock.
I believe the large (blue) hand advances one mark
around the perimeter for every engine hour.
In 60 hours, the large hand will accomplish
an entire circuit of the gauge.
The little hand (white) keeps track of the
number of 60 hour increments.
I think the meter reads 505 hours.

I think you're right, except the white hand is a minute hand. (I should have
mentioned that it moves one RPM.) The little green hand that's partially
visible behind it is the slow hand, I think. Notice that it's pointing on
the 480 side of the space between 480 and 540. I would think that it should
be closer to halfway, but maybe that's an illusion.

Any idea what the pattern of blue tick marks indicates?