Blood & Treasure doesn't try to emulate OD&D like the above two, but it certainly has it's feet roots in the OSR.
There is nothing that Thieves can do in Blood & Treasure, skill-wise, that every other class can't do. Thieves just do it better - much better.
Here's how skills, or "Heroic Tasks" work in Blood & Treasure:
If you are unskilled, you need to roll an 18 or better, but you can add your stat modifier to the roll.
If you have a "knack", like elves finding secret doors, your target is 15 and you can add your stat modifier.
If you are skilled, like a thief with finding traps or hiding in shadows, your target is your relevant save. You get to add your stat modifier to the roll.
I like it. I like it a lot.
I liked how Crypts & Things handled it, but this one goes to "Eleven" in usability.
Even if I never play Blood & Treasure (and with the number of OSR games I own, it's possible) I'll be porting this over to my next game, not matter the system. It really is that good.
The fact that the different task descriptions include examples that would elevate the difficulty, thereby imposing a penalty on the die roll is just icing on the cake.
Guess I still need to cover the rest of the classes next, don't i?