It is hard for me to give a opinion based on these pictures.
It is hard to tell if this is a proof coin and if the mint mark is missing or has
been altered in some way.
A 1971 no "S" proof nickel would have come from the San Francisco
mint in a hard plastic holder inside a blue cardboard holder.
If the coin is a mint state/business strike coin, then
no mint markwould mean it was struck in Philadelphia.