They are parts of an iron "Smokehouse type" padlock's body... specifically:
the back,
the front with a swiveling brass keyhole-cover,
a portion of the "side frame" (which went in between the front and back),
and a piece of the bottom of the keyhole.
The photo below will help you visualize how the parts you found fit together.
Lacking a maker's-mark on the brass keyhole-cover, your lock is difficult to time-date. The "Smokehouse" type was manufactured from the mid-1700s into the early 20th-Century.
That being said... carefully clean the encrustation of the keyhole-cover, and look for markings. Examples of commonly-seen keyhole-cover markings are the word "Patent" and/or a British Royal crown, usually with the letters VR or GR near the crown.
