I'm getting two of these most days, so the most likely candidates are:
Black Australorp
Buff Orpington
Gold-Laced Wyandotte
Brahma (1 Light, 1 Dark)
Speckled Sussex
Other breeds in the same flock:
Plymouth Rock (2 Barred, 1 Partidge, 1 White, 2 mixed)
New Hampshire
Delaware
I wonder if it's possible these two off-color Barred Rocks might actually be off-spec Marans instead? We actually had ordered Cuckoo Marans but got 2 Partridge Rocks instead, one cockerel and one pullet.