While there is no way for the average coin collector to find a date on a very worn coin the mint mark can narrow it down.
Knowing the mint mark is from San Fransisco narrows it down to 20 possible nickels. Most have average value but a few like 1915 and 1921 are $50+ in low grades.
Here's the stats...
Type/Country: 5 Cents / United States
Metal: 75% Copper, 25% Nickel
Value: $0.50 in G-4
Do you have an old nickel and want to know its value? Leave a comment/question and I will do
my best to find out the price and history for you.