Rare because they didn't sell many of them. But rare doesn't mean valuable. As there's no clamoring or much demand for any of the Eagle brand razors, there's not many people out there looking for an empty case. But anything's possible... And welcome to TSD.
Will the Gillette kit items fit into the Eagle box? If they do, and the Eagle box is in excellent shape it may be desirable as something that one actually uses.