These came in an cheap worldwide lot I bought on
ebay. Only information I have so far is that they may be from Plantsville, Conn.
They depict a fly, star and Indian, some in magenta, some in black. I've spotted a couple covers via Google (quite expensive, actually), but have not seen stand alone blocks or anything.
Any information, such as background, would be greatly appreciated.

The block of 6, at the bottom, with the town handstamped is a precancel.