Dead Letter Box?

near Humboldt, Minnesota approximately 2018 My brother-in-law knows that I like taking photos of unusual things, so he shared this photo, taken near Humboldt, MN. Since he didn't know the story behind the mailbox, I did an online search and discovered the following on a Geo-cache site: "One day we were driving by this little cemetery and I noticed something odd...a mail box? I called my Dad and asked him what that was all about, and he didn't know. He said to call my uncle who is on the township board. My uncle told me that a local couple placed the mailbox here and left a guest book inside for visitors to sign. They also placed the sign. We thought this would be a neat spot for a cache, and I was given permission to place one." Purpleturtles3