They received an order with a name and address. They send the item to that name and address. Marina confirms that Oswald obtained a rifle in that same timeframe. The rifle found in the TSBD has the same serial number as the one Klein's sent to Oswald. I'm not even sure what you mean by "proof of shipment". There was no requirement in 1963 that I'm aware of that would require any such record. Do you believe that Klein's was required to keep any such "proof"? If not, you are just suggesting that they should have complied with some imaginary best business practice that you have conjured up nearly six decades after the event.
Thank you for not answering my question.
Do you believe that Klein's was required to keep any such "proof"? Required by whom? They would be utter fools and very quickly out of business if they didn't keep some sort of postal receipt to show that a particular item was send to a particular client or address. Just imagine the free for all as a result of a lack of such proof of shipment; anybody could order something, receive it and then claim their money back by pretending they never received it.