so hard to guess any dogs age.
I rescued a DoberGirl a few years ago, from the teeth they guessed 3 or 4 years of age. But, as soon as I saw her I knew she was older, just because I have owned quite a few Dobergirls over the years and you sorta get to know how they age.
She was heavy in the loin, soft topline and had a wisdom in her eyes that could only come from years of living. Her feet were starting to flatten, a little grey in the muzzle, etc.
But unless they were registered, there is no way of knowing for sure how old they really are.
Can you post some pictures of your Heidi?
And may I say.....Bless you for bringing a rescue Doberman into your heart and home!!
Rescues are the BEST!!!