Please check your bill again. "B" is the highest series letter for a 1957 $1 silver certificate.
In any case these bills are common regardless of series letter. In average condition they retail for $1.25 to $1.75.
As of 01/2013 a 1957 A blue-seal $1 bill is worth about $1.50 in average condition, and $3 in uncirculated condition.
The blue ink indicates the bill is a silver certificate, a form of paper money that could be exchanged for an equivalent amount of silver. Printing of silver certificates was discontinued in the mid-1960s and redemption for silver ended in 1968.
At least one dollar
Please check your bill again. It's a $1 bill; the blue seal indicates it's a silver certificate. There's more information at the Related Question.
Please check your bill again and post a new, separate question. There were no 1957 $5 bills, only $1 bills, and they all have blue seals.
Please check your bill again and post a new, separate question. Only $1 bills were printed with the 1957 date and they were blue-seal silver certificates.
All silver certificates printed from 1928 to 1957 had blue seals. Please see the question "What is the value of a 1957 A US 1 dollar silver certificate?" for more information.
At least one dollar
Whats the value of a 1935g one dollar bill with blue writing on it
Please check your bill again. It's a $1 bill; the blue seal indicates it's a silver certificate. There's more information at the Related Question.
Please check your bill again and post a new, separate question. There were no 1957 $5 bills, only $1 bills, and they all have blue seals.
Please check your bill again and post a new, separate question. Only $1 bills were printed with the 1957 date and they were blue-seal silver certificates.
All silver certificates printed from 1928 to 1957 had blue seals. Please see the question "What is the value of a 1957 A US 1 dollar silver certificate?" for more information.
One dollar and 27 cents.
The blue seal indicates your bill is a silver certificate, a form of paper money issued until the 1957 series. Please see the Related Question for more information.
Please check your bill again and post a new, separate question. No US bills are dated 1937. 1935 and 1957 are the closest dates for blue-seal $1 bills
These are very common among collectors and sell for about $1.25
Please check your bill and post a new, separate question. The US didn't print any bills dated 1965, and the last blue-seal $1 bills were in the 1957 series.
5 dollars