Riddle 6

My first in childhood is unknown,
To us ’tis by experience shown;
It has a prominent position
Wherever there ’s an Exhibition.

My last, though old and like to die,
Perhaps possessing but one eye;
Are of small value, people say,
And pass them carelessly each day.
D stands for them, and I have found
Them often in the common pound.

My whole, men struggle to control,
And with my last they meet my whole.