The reason for this is as follows: (especialy for $20s)
UNC bricks of $20s are hard to access. Currently, as Gilles points out in his recent letter, there are about 5 or 6 people who have regular "brick search" access to them
across the country.Even though the ranges are not the smallest, the number of UNC notes recovered from bricks is staggeringly low.
For example, EZL, the rangs are 360,000 and 270,000. However, the number of UNC notes ever found remains in the neighborhod of about 20-25 or so.
Always a good point to keep in mind when searching-- how many were recovered.
Just like 1937 radars. We know they were also every 1000 notes. BUT, few were put away, thus the prive drive we have sen in them. How many were found in UNC? I don't know. Imagine if you had one, what do you think fair market price would be?
Anyway... I just wanted to give some context to Oli's post.