This popular 3 cent pattern employs an obverse die created from the coronet large cent design of 1840-1857. They were made at numerous times on planchets of various thicknesses.
The following notation is from George Eckfeldt's journal.
"Struck a few 3 cent pieces of copper & zinc; the size, thickness and diameter about that of the 1857 copper cent. About the middle of 1863."
In copper, as illustrated above, there are about 50-60 known. Full red examples are rare.
They were also struck in aluminum J320/P385 supposedly on both thick and thin planchets. These are much rarer with the following 5 confirmed:
1) Mitchelson, Connecticut State Library - gem proof
2) Garrett II-Bowers & Ruddy 3/80, Hughes 7/80, Denali - PCGS66 vertical mark in hair visible on all plates.
3) B/M 1/97, Southern collection, Simpson collection - PCGS64.
4) ex Bourne - PCGS63.
5) Woodin, Newcomer, unknown intermediaries, Heritage 2/06, Saul Teichman - NCS60 with laminations. This is plated in both Adams and Woodin and Judd 10th edition, illustrated below.
Photos courtesy of Heritage.
Eckfeldt journal image courtesy of Alan Meghrig.