I noticed this challenge last night when I decided to come to the CITO today. However I didn't realise that there was a checker so I dismissed it from my mind thinking that I didn't have time to see whether I qualified or not (I suspected that I didn't).
This morning I was walking around litter picking with some other cachers and mentioned it to bleachedwestie. She said she knew she would qualify as she had done the mystery 101 series in a day and they start with the letters A-Z and the numbers 0-9 (36 caches in all). I remembered that I had done all but three of them in a day but which were they?
We had no problems finding the cache as Team Kiisseli were just coming out of the undergrowth after putting it back - it was still swinging so very easy to spot. I signed the log and crossed my fingers hoping that the three I had DNFed that day weren't any of the letters I required for the challenge. I was very pleased when I got home just now, and ran the checker to find that I am indeed qualified.
colincactus has used Project-GC to see if he qualified for this challenge and he did.
M: GC5ATN6: M – Mystery 101 (Roots),
B: GC5AT7H: B – Mystery 101 (I Put a Spell on You),
T: GC5ATX6: T – Mystery 101 (And another thing…),
K: GC5ATJE: K – Mystery 101 (Deaf as a post),
Z: GC5AV0P: Z – Mystery 101 (Mosaic Five),
All found on 24-Aug-2014. I'll add more details here.