The Twelve Days of Christmas as written by =Twinkle.
For each day find the difference between =Twinkle's version and the correct version. Ignore the number (or the first "A" for day 1) and convert the letters to numbers in the most obvious way.
The cache can be found at:
N 51 (sixth).(seventh)(tenth)(twelfth/(seventh+eighth))
W 000 (second-first+ninth).(ninth-first)(eighth-1)(seventh+1)
There are certificates for the first 9 finders and a small stocking filler type prize for the FTF. As an added incentive (or if you like Christmas present), I have included hints for a few of my lesser solved puzzles: Bump!, GC Code, and There and Back Again in the Geocheck page.
My thanks to mashworth for being my ever patient cache test dummy