Unusual find, in my backyard!!

I've been doing some garden expansions the past few years, combining smaller gardens into larger ones and as the shrubs and trees grow larger, expanding the gardens around them. I do this mostly, to make my husband's job easier. He uses the lawn tractor and often gets hit in the face by growing trees and shrubs.

Last year I came across this little piece of pottery, while expanding one of the gardens. We know from stories and from seeing the several rock piles throughout the property,  that other people lived here many years ago. We    built, 39 years ago and before that it was pasture land.

Last year I came across this tiny piece of china. It had

 definitive markings on it, with the lions head and the unicorn in the blue and what appears to be a crown in the middle. I could find little about this small piece. I'm hoping to find another like it to  make a set of unique earrings for myself.

This is the front side of the hoe.

Today, I found this, when expanding another garden. This garden is located around a large rock that was used as a containment spot for other displaced rocks. It has become my rock garden. 

My quick research tells me it is called  an 'Antebellum Blacksmith Made Plantation Hoe'.

Antebellum, meaning after the War of 1812 and before the Revolutionary War. That puts it between 1815 - 1861, probably made in the U. S. A.

But it was found here in Canada, in southern New Brunswick, near the banks of Darling's Lake, leading to the Hammond River, then to the Kennebcasis River and on to the Saint John River.  In older times, I've been told, people traveled the rivers rather than the roads.

This is the backside of the hoe.

At first I thought it was a split stone and was going to to toss it in the wagon to go to the yard waste pile, until I saw the handle, opening. I am very anxious to learn more about this piece of gardening tool; when it may have been left and how long it has been in the ground.

 I also would like to know how to preserve it, now that in exposed to the air. I have cleaned the excess dirt from it with soap and water and a soft brush. I have it in a freezer bag and out of the sun and away from the  air.
If anyone can identify this or has any suggestions as to how I should proceed from here, I am open for suggestions.