There is a cancellation stamp on the item...knowing the date might help. I can't make it out.
It certainly looks like someone at 601 Nassaua Street knew Lee Oswald, and knew that he had an address in Irving.... because it was forwarded to Irving Texas.
If someone had sent Lee the package ( the hand writing looks like Lee Oswald's) when it was received at the Nassaua street address and forwarded to Irving then the only way Lee could receive that package would be for him to go to the Irving PO and ask if there was anything in the dead letter bin that was addressed to him.