Do you believe that bag was used in the ordinary course of TSBD business to wrap books or not? It's a simple question.
The honest answer is that I have no idea, and nor do you! Although it seems unlikely that the purpose of the bag was to wrap books. It doesn't even matter, because if the bag was not used for ordinary TSBD business, it still doesn't mean that it must have have been used to bring in the MC rifle.
Unless you can show that the bag was used to bring in the MC rifle, all you have is an insignificant bag, made from TSBD materials and found at the TSBD, with multiple unidentified prints on it and allegedly two prints belonging to Oswald, who happened to work at the TSBD.
So, before you start jumping to flawed conclusions, you might want to consider the possibility that somebody else, other than Oswald, made the bag, for whatever reason, and that some of the other prints got on the bag when people picked it up to move it. You also may want to consider why Lt Day made a duplicate bag and who sent a similar bag in the mail to Oswald at a non-existing address.