Watch for the Sanford Community Garden sign (waypoint listed) and turn down the dirt road past the McKeon's private gardens, a real treat when in bloom. The McKeon Reserve hosts the Community Garden as well as having a variety of natural features and trails under various stages of development. These trails, marked with signs and maps, lead to the Springvale Rail Trail and provide a closer route (than the Hanson's Ridge Trailhead marked byThe Dip cache) for many of the Rail Trail caches.
You are looking for a dark preform on a kame. Topographically, a kame is a relatively small long mound of natural material. It is the smaller "cousin" of an esker. You'll only be able to unscrew the cap. Don't forget something with which to write!