RN300-MT QS120-DD.
Cabot Watch Company Quartz Divers' Watch. Brushed matte top with polished sides and back as per the issue watch, but with the added day/date function.

Swiss-made, Ronda 517 quartz movement. Sapphire glass, anti-glare. One-way time elapse bezel, 120-click.
Water-resistant to 30 atmospheres, 300m.
Matte finish stainless steel case. Screw down crown. Screw down caseback. Fixed strap bars. Battery life indicator. Luminova markings. Day-date function.
Weight (without strap): 70g

Supplied with 20mm grey strap.