Actually, I owe sonny60 an apology and here it is...
What you found is DEFINITELY a Federal made and issued "official" Caltrop.
I did some additional research and discovered that the Federals did indeed coat their Caltrops with "White Metal" which was either tin or pewter and that they had blunt points rather than the sharp ones I found in Tennesse related to the battle of Franklin, TN.
My caltrops were sharp pointed and of iron only and.... were apparently of CONFEDERATE origin... not Union.
So, your caltrop is a fine example of plated iron and worth, on the retail market, as much as $125.00.
My hearty congratulations on a great and rare (for Kentucky) Civil War artifact!
DC
PS~ The theory behind the blunt vs. sharp points on the caltrops was apparently this:
The blunt point was designed to cause a "stone bruise" type injury without actually sticking in the horses hoof tissue. It would immediately slow the horse down but not necessarily stop him completely at that moment. This way the horse would be crippled for days and the caltrop would remain in the road to present the same threat to the horses following. The sharp pointed caltrops would stick in the horses hoof and force the horse to stop immediately and the rider would have to dismount and extract the caltrop from the hoof. While it took the horse and rider out of immediate pursuit that particular caltrop would not pose any threat to the other horses and riders following.