County System

Colorado intentionally ships out certain allotments to counties. While not a "true" county system like Idaho or Wyoming, who use county codes, it's more of a "huge set of plates in order that is definitely noticeable". I like to think of it as the 1982 CO county system, with a bunch of random little sets instead of larger, officially published ones. Some states ship out blocks of plates in sequential order, but they're nowhere near to the extent of CO's blocks, which are often tens of thousands of plates large.

The true, solidifying evidence that CO intentionally distributed plates to counties in this way is through their non-pass types. All the plates that aren't POD at an office always line up with a passenger allotment. Though it is worth noting that some passenger allotments are more important than others; typically only the largest allotments receive other types of plates. One such allotment was Eagle County's BZC-BZG set, which was one of our largest, and it had many different associated types - see pics below.

Some counties are harder to find allotments for than others. My Eagle list is extensive and very accurate, but that's only because I live here. Some plates, especially ones from the 2000s, are mostly off the road and it's very difficult to get full, accurate allotments. Meanwhile, I see the new format allotments all the time, and can easily pin those down.