Trackmaster Knapford Station Question

I never had one, but I can tell that part is not a battery cover. If it were, it would've had a screw and the word "open" with one or two arrows embossed on it. However, the old Motor Road and Rail Cranky had a large crate as the battery cover, with no such indication. No special feature is advertised on any of the boxes this came in, so it's most likely just a removable piece that happens to have that tab.