[Porscha]

My Husband and I got our Rottie through a friend of a friend. We weren't planning on getting a pure bred pup or any pup at all when we got our Rottie Porscha. We knew we wanted a pup in about a month or so but a situation arose that we couldn't turn down. A friend of the family (not one that I know however) had a litter of pure bred rotties. I am not sure why but they offered one to us for free. Aparently they heard through the grape vine that we were thinking/looking at getting a pup. Long story short we got a female rottie "pure bred" pup from this family for free.
My husband and I are both skeptical as to whether she is actually a pure bred Rottie. (not that it matters she is awesome! were just curious)

She is about 8-9 months now we figure, as we aren't sure what her exact birth date is. She is about 88lbs, now.
Her tail is docked.
She looks very Rottie, except for her markings. Instead of the rottie brown, she has brindle in the rottie pattern (if that makes sense). And when she was younger she had a small tuff of white hair on her chest, not quite the size penny. She still has a few white hairs on her chest but they are almost impossible to find now.

Does anyone know why her markings are like this?
We saw one of her brothers when we picked her up, he had the rottie colors but she didn't. .....