list of devices
How can i see a list of my purchases that ALSO shows which device was being used for the initial download/purchase authorization
iPad (4th gen) Wi-Fi + Cellular, iOS 9
You can view your account's full purchase history via your computer's iTunes : See your purchase history in the iTunes Store - Apple Support
On your iPad you can view the last 90 days purchases via http://reportaproblem.apple.com
You can't see which device or computer's iTunes did the purchase.