Writing your own iTunes IAP server authentication, unique details in receipt?

I am trying to check my own receipts for IAP. I ran into several issues in finding a persistent data point that I can check for uniqueness.

The first problem is a lot of my receipts status: 0

however the field in_app

is an empty array. So no transaction_id, original_transaction_id

.

I've seen this question asked here and on the Apple support forums, but haven't seen any definitive or formal answers to these types of receipts - they are valid, etc.

The second problem is finding a unique data point. If we ignore the empty field case in_app

and only take receipts from transaction_id

.

Is there any legitimate scenario where a transaction_id

appears twice? Or is it a verified fake receipt?