The large fowl white Barnevelder was produced by crossing with a white Rock in the early 1930's.
They are available and relatively common in the European Union but not in the UK or the US.
Below: A white Barnevelder male.
White Barnevelders should be pure white with no yellowing in the feathers and no spotting or dark colours. They should have the characteristic bright yellow legs, shape and stance.
Below: A white large fowl Barnevelder hen.
Notice the classic shape , yellow legs and finer comb.
The bantam white Barnevelder :
Bred in the 1950's from black Barnevelders and white Wyandottes.
Below: A white bantam hen.
The white comes in both bantam and large fowl size and was not a standard in the breed until the 1960's.