Download an app to view the A9 processor version. Download an App called \"Lirum Device Info Lite\" from the Apple App Store. Simply open the software, you can check the phone's system information.
The version of the A9 processor can be found by looking at the Model number in Storage and Model Information. The model number corresponds to the following:
iPhone 6S: N71AP - Samsung N71MAP - TSMC iPhone 6S Plus: N66AP - Samsung N66MAP - TSMC