Heavy metal in the hay field across from my home

It has been wet, cold and overcast for weeks here in Maine, but finally I saw a little sun late this afternoon and decided to wander off into the 50 acre hay field across from my home.  I started by going around the edge, following the tree line and that's where I turned up the big horse shoe.  And I found some other assorted bit of farm equipment as I wandered across the field.  It was really muddy!

Here's the view from the far side of the field looking back at my home.

And a couple of closer views of the horseshoe right after I hosed it off.

 I don't know anything about horseshoes, but this seems really old.  The field has probably been in active use for well over 200 years.  I welcome any comments about this style of horse shoe.

 Thanks to a knowledgeable Facebook friend, it appears to be from a draft horse with 3 screw type calks remaining on it.