i think in this case there is probably only 3 options:
1. use it to find out, as the difference in the edge holding ability should be big enough to tell the difference.
2. return it and buy a new one and explicitly ask for the one with XHP marking
3. send it to CS and they can probably tell you which model this is.
Also, there are minor change in the lockbar pin location in many of 2015 models, not sure if Talwar XL is one of them. You can find a picture of a pre 2015 version of the XL talwar online and compare it with your knife. If the pin location is different, then you may have newer one.
This is why I only buy the black coated version of 2015 models as the DLC coating is day and night from the old teflon coating.