Answer:
I am commonly abbreviated to H
There is one in a minute two in a moment and none in a thousand years. What is it?
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. Sooner or later everybody needs my help yet many people are afraid to let me help them.
I do not contain flesh feather or scales; yet I have fingers and thumbs.
What kind of dog keeps the best time?
When is it bad luck to see a black cat?