So you guys are talking about circulation finds then. I don't normally look at serial numbers that I use, but about a year ago, I was needing a coke, and for some reason I did look at the one dollar bill before I inserted it in the coke machine. Serial# 00000007. Don't recall the prefix or suffix though.
The note below had a fairly low printing in 1928. A one year type, the only small size red seal $1 note. Only in VF condition, but it is what it is.
Here is a $1 note that relates (somewhat) to the story in the link that Bobby supplied. I got it about three years ago. This note is series #1, serial #3310 (the 3310th one dollar bill issued by the US Government). There are five known $1 notes that were printed before this one, including serial# 1 (EF condition) which I have seen pictures of.