Odd sized WW2 American flag with 30 stars?

I just bought a WW2 American flag in France. It wasnt until I got home that I unfolded it and realized its odd size. It is probably about 3' by 8' and has 30 stars on it. On the edge is written 'Special Navy.' I hope this is a flag from a ship, and I hope I didn't get jipped. Can you tell me anything about this?