With all the apartment windows surrounding this cache and the busy street, you will have to be very sneaky to grab it without being noticed.
For a different "watch" experience, take a nice walk nearby to the historic Watch Factory where once upon a time, the most accurate watches in the world were made. You might even say that Waltham put watches on the map (too corny?). Watch factory employees used to have picnics on the Charles River behind the factory.