Info On Later 1957 Silver Certificates

Hello Community !

I just found interest in the 1957 silver certificates. Specifically in the few ones that have a SN ending in B, which just appears in the 1957 series (not in the 1957A or 1957B). I've read in my old Friedberg that the whole 1957 series had 2.609.600.000 notes printed (excluding stars). So my first thought was:

"There are 26 letters in the alphabet. Every block starts with a new letter. AA beeing the first and ZA the last. That should be 2.600.000.000 notes ending with an A. Making only 9.600.000 notes ending in B. Right?"

Wrong. I had my first scepsis, when I found a note that had a A1...B serial number. As the highest, I thought, should be A09600000B. Maybe they skipped some notes? Then I found a A4...B and finally even a B..B.

This was, when I learned that there are no SN starting with an O. I guess it looks to much like a zero. So there are only 25 A-blocks and two B-blocks: a complete AB and the very small BB. Well nonetheless I like my 1957 silver "B"s and I have yet to get a BB.

There is currently a BB up for sale on ebay. Price is 130$ and I'm not sure if this is overpriced? Can't find that much info on these notes. I appreciate any input.