Hey- just an FYI those marks are primarily for the fire dept to use. The number is the street address, the blank red box means it's vacant, so we know there's less likelyhood of anyone being inside minus squatters. One hash mark through the box means it's hazardous inside and use extreme caution- make entry only if necessary i.e. witnesses are reporting someone trapped inside. Two hashes or the "x" means that it's vacant, been emptied of anything of value and structurally extremely hazardous, and should not be entered at all. Basically that way we don't risk anyone's life searching a building that's verified vacant, and of no value to save; we can set up an exterior operation. The red box with "x" is also called an "A.G.O." which stood for "All Goodies Out" and was what the building inspectors in NYC used to use to inform squatters and vandals that there was nothing worth looting in vacant buildings that were dangerous to enter. Then the fire dept started using the above system as it became unified- at least in NY and NJ I'm not sure about the rest of the US.

It's a downrigger or planer for fishing. When you're trolling it will act like a waterfoil to keep the rig a a specified depth that matches the preference of whatever species you're attempting to catch. It's an old one though for the record, the newer ones are a little more complex.