Glad you got to see the barbecue my father built. I am trying to get my older brother, Alex (Sandy) to give me more accurate information, since I was only about two or three when the barbecue was built.
I do remember that the stones were from the Main Street area at the intersection with Poplar Ave, and may have been removed as part of the re-configuring of the intersection.
The slate patio in front of the barbecue was made from sidewalk slate that was removed as the sidewalks were changed over to concrete. When I was a kid, many of the properties along Poplar Ave still had slate sidewalks, and they weren't easy to skate on... That may be another piece of slate to the left of the barbecue.
I'm not sure if the round stone was local, or if we brought it back from New Hampshire where we used to spend our summers. I know there was no stone on the property, because as kids we used to dig forts and underground tunnels all over the backyard, and all that was there was sand and clay. My father, Alex, had a connection to New Hampshire in that right out of college he was a member of the first crew of the Mount Washington Observatory, and in 1934, he and two others, recorded the highest wind ever directly measured by man, 231 MPH. We had a cabin in NH so maybe we brought the stones home from there.
We lived in Hackensack from around 1946 until my parents retired and sold the house around 1975.