I'm going to guess that it was a fake made to fool someone in the past. The drill holes and the file mark on the side is where they tested and checked it out. It looks like brass, but polished up ? Might fool someone pretty easily in the past. I've seen real bars that had been "drilled and filled" both gold and silver. Nowadays, they can be tested pretty quickly without even scratching them, but in the past it was probably easier to get away with.
Or like mentioned above, maybe a prop or paperweight. But I've made some big mistakes when buying and have known others do it too. The greed will get ya and you overlook the obvious sometimes.