Terry:
Great find. Lefever sideplates in 20 ga. are scarce as hen's teeth in any grade. If you can find a 20, they are most often a DS grade. They are universally sought after by everyone, especially with 28" bbls. I looked for years to find one.
TT gave some great info. A few other notes: The Durston family took over Lefever Arms in 1901 when Uncle Dan departed, and introduced the DS and I grades shortly thereafter. All DS grades had fluid steel barrels.
I would suggest getting a copy of the book, "Uncle Dan Lefever, Master Gunmaker" by Bob Elliot. It's a great book and will add to your enjoyment and appreciation of the gun. According to the s/n chart your gun dates about 1912.
Congratulations!
Bill
