A 1957 blue seal silver certificate is probably worth only a small amount over face value. According to Heritage Auctions, an uncirculated bill is worth between $2 and $4, and a circulated bill is worth between $1.25 to $1.50.
However, if the serial number has a star after it, the value will be somewhat higher. According to experts, if the 1957 blue seal silver certificate star note is in average condition, it would be worth $3. The value would increase to about $10 each if one had a large amount of these bills in uncirculated condition with consecutive serial numbers.