Outdoor Field is the sub-type that takes the plain, legible language of a classic field watch and hardens it for real backcountry use. The distinction is not the military-style dial, it is the durability spec: sapphire crystal, a screw-down crown, water resistance that usually starts at 100 metres, lume you can actually read at a glance, and frequently field-useful additions like a compass, altimeter or barometer. The big numerals and clean hands inherited from 1940s field watches stay, but the cases are deliberately built to shrug off knocks and moisture.
The examples run across every budget. The Hamilton Khaki Field Expedition Auto comes in 37mm and 41mm with a screw-down crown, Super-LumiNova, 100m water resistance and the 80-hour H-10 movement, landing around £800 to £1,000, with the 37mm blue dial near £950. The Timex Expedition North Titanium Automatic gives you a mechanical outdoor entry in bead-blasted titanium with sapphire and 200m water resistance for roughly £280, with a GMT version near £440. The 41mm Marathon Navigator pairs sapphire with 100 metres of water resistance for about £320 to £390. At the tougher end sit the titanium Bertucci A-4T at 200 metres, the Luminox Atacama at 200 metres, and the Victorinox I.N.O.X. at 200 metres; the Casio G-Shock GWG-2000 Mudmaster packs solar quartz with a compass, altimeter, barometer and thermometer. Garmin's entry Instinct starts near £240, with the current Instinct Solar near £320.
When you choose, start with how you actually use it. If you are genuinely on mountains, in water and through mud, sapphire, a screw-down crown and at least 100 metres of water resistance are non-negotiable, and a titanium case earns its keep on long hikes by sitting light on the wrist. Mechanical versus quartz versus solar comes down to wear frequency: occasional users are better served by Eco-Drive or solar that needs no winding, while daily wearers will enjoy an automatic like the Hamilton. ABC-sensor digitals give you the most function, but do not expect the simplicity or longevity of a clean analogue tool.
One nuance worth keeping in mind: outdoor field is not a single thing. At one end you have mechanical, analogue, field-prepped classics like Hamilton and Marathon; at the other, sensor-loaded digital tools like Garmin and G-Shock. For most collectors the sweet spot is a rugged but understated analogue that works at camp and at the office alike.