Three Dollar Gold Pieces article by Seth Chandler
Seth Chandler's featured article on this PCGS website merits a read. While it focuses primarily on the pristine 1863 piece from the year of Lincoln's Emancipation Proclamation it was instructive to learn that Lincoln had a role in low mintages that have resulted in the scarcity of $3 Dollar Gold Pieces in subsequent years. Check out the article for the Lincoln connection.
The other take away that I found surprising was that for that year PCGS has only graded 50 $3 Gold Pieces in total as mint state. Likely many of those were resubmissions so the actual number is undoubtably less.
I had always felt that my own 1864 $3 Gold Piece, PCGS graded MS64, minted the year after the one described in Seth's article was special but I had not realized its mintage of 2,630 was almost half of that of the preceding year's $3 gold pieces which included the one that Seth featured in the subject article. Similarly the PCGS mint state graded coins for the subsequent year were limited. Only 11 coins for 1864 have been graded MS64 or higher and again likely some of those were resubmissions so the actual number is undoubtably less.