I have a chick that's a nankin / sort of ginger red old English game with brown under fluff cross that looks almost identical to that chick. It didn't look like the tiny baby one when it hatched, but the older one it used to look just like it. It recently changed from looking just like your chick to a really pretty orange-ish golden-ish gingery color with tiny light brown v shapes on its saddle and black under fluff. It's a beautiful pullet though.The Buff partridge chick actually feathered a out alot the same as Topaz, one of my Project Wheaten Crele Orpington chicks.
View attachment 2738920View attachment 2738922Both have Black down/Under Fluff. Topaz is now an adult though.