In honor of the newly released Whitebox OD&D pdfs, let's take a look at the first class added to those rules: the Thief. Not the commonly known version in the 1975 Greyhawk supplement, but the even earlier one in the Great Plains Game Players Newsletter (May 1974), from just a few months after those first D&D sets were released. Jon Peterson helpfully shared this material with us in a post back in 2012.
As Gygax acknowledges in the article, he got the idea from a phone conversation with Gary Switzer, owner of Aero Hobbies in LA, "who mentioned that his group was developing a new class of character -- thieves" and "gave me a few details of how they were considering this character type, and from these I have constructed tentative rules for this class". In Switzer's group the original idea was by D. Daniel Wagner, who talks about it here in the OD&D Discussion Forums. Wagner later co-wrote the Manual of Aurania, and a few years ago he let me post some of the Aurania material on the blog here.
The "Great Plains Thief" very much resembles the Greyhawk thief, but there are differences. In general the original version has less limitations and is more forgiving (less chances for failure). Furthermore, the write-up provides examples and clarifications on the second page that are not found in Greyhawk.
-Hit Dice. Most notably, the Great Plains Thief uses the original d6 system for hit dice, where all classes use d6s. For the thief this means 1d6 at level 1, 1d6+1 HD at level 2, 2d6 at level 3, etc. This really gives this version a "LBB" feel. Greyhawk only presents thieves using the "alternate hit dice" where they get a d4 hit dice per level.
-Alignment. The Great Plains Thief is "always neutral". The Greyhawk version adds chaotic to this, plus a note that lawful characters can employ them on a limited basis for missions.
-Armor. The original write-up lacks the clarifying note found in Greyhawk that shields are not allowed, thus rendering it ambiguous whether they can use shields.
-Climb Walls. The Great Plains Thief has this ability, described as "Climb almost sheer surfaces rapidly, up or down", but no chances are given, implying it is automatic. Greyhawk introduces a chance of failure (13% at level 1).
-No "Pick Pockets". A skill of this type is present in the original write-up but does not yet have its standard name; instead it is "Steal items by stealth and/or sleight-of-hand", which to me implies a broader skill than just "picking pockets". Furthermore, this ability is not listed in the table of chances; instead the example on the second page indicates that the chance is the same as move silently. In Greyhawk it was changed to "filch items and pick pockets" in the list of skills and just "Pickpocket" in the table, where it is still given a chance equivalent to move silently.
-Finding Traps is automatic. Notably, in the example in the original write-up the thief finds traps in two chests simply by examining them, without any rolling. Only removal requires a roll, with failure activating "it with regard to the thief and any others within its range". This idea would persist into Greyhawk, Holmes Basic and Moldvay Basic where there is a "Remove Traps" but no "Find Traps" skill for thieves.
-Open locks saves time. In the original example, Gygax notes that failure to open a lock means that it "must be forced open - a very time consuming process". Also note that both here and in Greyhawk the skill is described as "by picking or even foiling magical closures". This is not explained further, but one could rule that this includes opening Hold Portal or Wizard Locked doors.
-Reading languages and scrolls are automatic. Greyhawk adds chances for failure, but that's not in the rules here.
-Hide in Shadows allows movement. The second page clarifies that is a chance to "remain undetected when hiding or moving through shadows" (so the thief doesn't have to remain still), requires shadows "of course", and a lack of "observation prior to hiding". In the example, the thief is able to avoid observation by a pursuing monster simply by hiding once the party goes around a corner.
To make the original material more usable for gaming, I've edited the material into a single page "Thieves Reference Sheet". I took the Holmes approach here, attempting to retain as many of Gygax's original words as possible. It's digest-sized (a 8.5 x 5.5 sheet), so it will fit inside your virtual or real Whitebox.