Tall stamped Chinese paneled vase with birds and flowers.

Here is another of my auction finds. I seem to be getting pulled towards Chinese vases lately!
This vase is 14 1/2" tall, 4 7/8" across the rim, 3 3/4" across the base and about 7" across at the widest section. The stamp on the bottom is about 1" square.
There is a triangle which seems to have been taken out of the glaze on the bottom for some reason.
I would love to hear from anyone who could tell me anything about this vase such as age, style, stamp translation, why the triangle is there, etc.
Thanks!