Markings on Schnauzer's butt - is this common?

by Marilyn
(Utah)

I have a black mini schnauzer puppy with phantom markings.
She has a silver gray diamond on her butt. It is a very well defined marking. It is about 2 1/2 inches.

She has very faint eyebrow markings, a little white hair in ears and front of back legs and a little silvery hair on lower front legs and a tiny amount on her cheeks. This is not white but silver gray. On her face it almost looks like it has been singed.

Do most minis have a light marking around their butt area?