The Schrade 5OT came out around 1990 and was available in carbon steel with green saw cut Derlin scales and a carbon steel blade. Occasionally, you'll see some of the green ones with stainless "Schrade +" blades. I actually have mine in my pocket today as it turns out. This picture is
not mine but gives you an idea of what they look like. The green scales take some getting used to. Blade is a tick under 3" and closed length is a tick under 4". Very thin and pockets nicely. There is an old version that has brown scales and Schrade+ stainless. Current Chinese made ones have the brown scales and 400 series stainless.
The GEC mini hunter model 72 is a current day (and pricey) option. They are available with a range of blade types.
Another current day alternative is the Boker "Tree Brand" Fellow.
Another older one that is harder to find is the Camillus "Gents Lockback" which was made with carbon steel blades.
The Bucks, while really nice are stainless blades.
I should note, while I really like my 5OT, find I end up carrying my Opinel #8 more often. It has a longer blade, weighs less and has a reasonably good lock (especially if you modify the lock ring with a file to allow it to spin more).