Steel Panerai Luminor 1950 8-Days Chrono Monopulsante GMT PAM 00311.

The start, stop and reset of the chronograph is operated by a single push piece at the bottom left of the case.
The second sweep sub-dial incorporates a small circular day/night indicator, which rolls to a full black circle from the dark night hours 6.00pm thru to 6.00am, and rolls to a full circle in day light hours, if flying to a different continent the hour hand can be adjusted independently using the winding crown to the arrival time-zone, leaving the 2nd black hour hand with luminous point set to the time zone of the departed country, the day/night detail indicated if the time would be for example 4.00am in the morning, or 4.00pm in the afternoon.