I am the GM at an Interstate Batteries distributor. I don't recognize the case style so I can't say who makes them for sure. They are probably a korean product if I were to guess. The built in hydrometer probably works fine but they only work for that one cell, and they only work when the fluid level is exactly correct. There is probably cell access under the sticker, or an entire vent manifold that can be pried off. It is good to be able to check the fluid level on lead deep cycle batteries, they will likely use some over time.
They seem priced very high for what appears to be a regular old 12v deep cycle battery. You could get an AGM battery for the prices I saw.
