The reason why this one has no checker is the fact that a checker can not know if a cache is from a serie.
This is the extra qualification in the challenge
Quote:
"Just to make it more interesting, the qualifying caches should only be traditional caches and
a maximum of four caches per series can be included, and 50% of the caches on the qualifying list should have elevations above 250 feet above sea level. So you can't go cheating and doing a hundred cache driveby series "