This cache is not at the posted coordinates. It is a bonus for the Concord's Revolutionary Black History Adventure Lab. To play this Adventure Lab, you will need a smart phone with the Adventure Lab mobile app installed. Completing each stage of the adventure will provide a journal entry containing a piece of the information needed to find this bonus cache. You'll find the cache near the Concord Depot, a stop on the Fitchburg railroad line, which opened in 1844 and played a role in the Underground Railroad.
This area is likely to have high muggle traffic, so please use the hint and your best stealth maneuvers. BYOP and tweezers!
Find the Bonus cache at: N42 27.ABC W071 21.ADE
Adventure Lab: https://adventurelab.page.link/84bn
Congratulations to Hypercycloid on the FTF!