This is a letterbox, please do not remove the stamp and ink. Thanks.
It is at the posted coordinates, but here are the letterbox instructions.
From the center of Goffstown, take route 13 north until you reach Black Brook Road on the right.
Take a right and travel down Black Brook road until you reach a stream crossing with guardrails.
Park a short distance beyond the guardrail on the left side. Now carefully walk back up the road along the guardrail on the right hand side, which will now be on your left as you are walking. The container is at the base of the guardrail at the end.