Reposting inline for you
at 201 days old the Burmilla chocs Dad, and therefore his older Mum, predate the release of the Halloween Collections and the discovery of Toyger Caramel, 200 days ago from today April 25th 2017 was 8th October 2016, both cats box opening predates that so therefore birth of the boxes also predates that making them pure. Fall Collections were released Oct 19th.
I think this will satisfy even the most ardant doubter that Burmilla Chocolate is indeed recessive to Toyger - Silver as at the time your Chocs parents were born it was the most recessive fur.
It might be helpful if you can post Berkeleys Pedigree as well as absolute proof that according to age of the line he is pure.