As legal tender, a dollar silver certificate is worth a dollar. Depending
on condition, there may be some numismatic value, but you'd have to sell it
to a collecter or dealer, you won't get more than a dollar from a bank. My
recollection is that silver certificates were last printed in the 1960's.
"Old" silver certificates (from the 1800's) may be worth considerably more
than face value.
Last series for the $1 Silver Certificate was 1957B printed in 1964.
Redemption in silver ended in 1968.
Unless it is in excellent condition it is not worth more than $1.
Sure it's in great shape. It's the first dollar he earned, borrowed,
purloined or was gifted.