Advanced Dungeons & Dragons (1977)
(the Player's Handbook and Dungeon Masters Guide were actually released in 1978 and 1979 respectively, but that's beside the point)
Initially things are much the same as previously, with the use of thief skills clarified, and general rules procedures still taking the place of many tasks today relegated to skills. There's this neat little bit where the first time a character listens at a door or other such situation, you roll to determine whether they have keen hearing, which thence gives a bonus to hearing things. There's also the possibility of hearing loss due to loud noises.
The only real addition is in the Dungeon Masters Guide with non-professional skills. And this is barely a system, really. You can just have 0-2 skills related to mundane professions, which may or may not come in handy.
But wait, there's actually more!
Oriental Adventures (1985)
Unfortunate name aside, this has to be one of my favourite old sourcebooks, but not for our subject today. No, today we aren't talking about the tables for generating yearly events, we're talking about non-weapon proficiencies!
As the setting was perhaps more concerned with courtly intrigues than dungeon adventures (still a wargaming activity if you ask me), characters were much more grounded than the traditional adventurer who was largely detached from regular society. And thus became necessary a more robust system for skills outside those used for exploring dungeons and fighting monsters.
This system works in conjunction with the weapon proficiencys system also introduced in AD&D, and the two actually share slots! So where a gaijin cleric would possess at 1st level only 2 proficiencies, to be dedicated to weapons, a shukenja of Kara-Tur would have a whopping 6, with the assumption that a number of these would be given to other skills. The proficiencies are divided into the categories of Artisan, Barbarian, Common, and Court. The barbarian class getting its own entire category probably explains why the class has the most number of proficiency slots, as no one else can learn the useful survival skills provided. The others merely require a certain environment to learn. Each proficiency simply has a chance of success, increasing with slots spent on the proficiency, though most can be used without rolling. If you're a blacksmith, you're assumed to be competent enough at your job, unless a work of superior quality is attempted. Some must always be rolled. These peaceful proficiencies can also be used for contests, which can award experience points!
A fun little optional rule grants characters bonuses on the use of peaceful proficiencies if the player can provide some suitable sample of the craft in question, like a Japanese poem or something. it's very silly, which is why it's strictly optional.
Dungeoneer's Survival Guide and Wilderness Survival Guide (1986)
These are books for perverts (me), with frankly stupid amounts of detailed procedure for their respective subjects. A system for ability checks is introduced, where you can accomplish various miscellaneous tasks by rolling under the relevant ability. But most importantly for our purposes, they expand on the non-weapon proficiency system from Oriental Adventures.
No longer are slots divided between the two types, now weapon and non-weapon proficiencies have their own. Sorry, barbarian weapon masters of yesteryear. The chance for success is also now tied to an ability, making this a sort of expansion on the previously mentioned ability check system, though again the majority don't require a roll in most situations. Proficiencies are divided into the categories of Craftsman and Adventuring (called Wilderness in the Wilderness Survival Guide).
Apparently the affliction of "not reading the rules" is older than you might think, so there are people who ask things like "can you not build a fire without the Fire-building proficiency?" Many of the proficiencies are skills that any character should be able to attempt, and indeed having the proficiency simply enhances your ability to do something that is otherwise covered in one of the stupidly detailed procedures of the books. For example, anyone can build a fire… assuming they have flint and tinder. A character with Fire-building can do so without such tools. But you'd better learn the Swimming proficiency if you want to swim, much like in real life.
Next time: there's two of them? This is getting out of hand!