Not sure it was mention but the plane registration seems to be B-1976 (Re: Q photo of airframe on tarmac)
https://www.radarbox24.com/data/registration/b-1976
https://www.planespotters.net/airframe/Boeing/737/B-1976-Air-China/0jQ4TJkQ
Hex Code 780C98 (lcao)
Delivered to Air China Oct 2014 so the photo dates to sometimes after that.