I know most US used stamp collectors prefer typically cancelled stamps or precancels, however, I've found it interesting to collect "box cancels" which can help to easily identify the location where the stamp was used.
I came upon this one recently. It's from a town in New Jersey that starts with the letters "Sing...". After some checking I found that the box cancel is from Singac, NJ (never heard of it) until I checked and found it to be a section of Little Falls, NJ:

Anyway, no post office is currently there, and upon checking Jim Forte's Postal History web site, it seems that the post office at Singac was only active from 1874-1937.
So it seems I have encountered a DPO (discontinued post office) box cancel. Not especially scarce, but certainly an unusual box cancel, as I don't recall having found many from DPO's before.
It just goes to show that box cancels can be fun to collect, too!