I'm certainly not an expert in amber. I would have a jeweler inspect the stem. It doesn't look like any amber I've seen. Which doesn't mean much. My experiences with amber was in Russia and all of the gems were polished and mounted.
The amber I've usually seen for pipe stems were of the yellowish or orange type. The stem on your pipe is very close, but has a lot more brown than I'm used to. This could attributed to the lighting used for the photo. It's worth an appraisal in my opinion.
I wouldn't begin to estimate the age of the pipe. I'm guessing that it wasn't smoked much, relatively little coloring, and lay, rattling around in a drawer for a while, judging from the myriad of small nicks.
Amber bit or not, antique or not you've got a nice pipe. God willing it will smoke as good as it looks.