Open a AMD SUPPORT - WARRANTY ticket (https://www.amd.com/en/forms/contact-us/support.html) and send in both of your new AMD Processor's Serial Numbers and Model number imprinted on top of the processor's lid.
They should be able to verify if both are authentic AMD Retail Box processors or not.
The link that @ardankyaosen gave is an excellent source to determine if the AMD Retail box you received is authentic or not.
NOTE: Both processors might be authentic except one is a Retail Processor and the other might be a OEM/TRAY Processor which is not covered by AMD 3 year Warranty. By the Serial Numbers AMD will be able to know if both are Retail Processors or not.