The popular Washington obverse design with the "Curved" 2 cents reverse. These were apparently struck late in 1863 as per the following notation in George Eckgeldt's journal.
Examples were struck as follows:
Copper/Bronze J305/P370 on both thin 78 grain and thick circa 92 grain planchets. Metallurgical testing has confirmed the existence of pure copper, bronze and copper-iron alloys. This a relatively common pattern with several dozen known but surprisingly rare in full red.
Copper-nickel J306/P371 with about a half dozen confirmed.
Oroide J307/P372. This may not actually exist as the Byron Reed example is now attributed as a J306/P371.
Aluminum J308/P373 with the folllowing 4 confirmed.
1) Byron Reed-Durham museum
2) Kaginís 4/75, Superior 8/04, Heritage 8/95 ANA, ANR 11/04, Heritage 8/07, B/M 8/10 as PCGS62 - PCGS63
3) Kreisberg-Schulman 4/59, Stacks 8/71 ANA, Smythe 10/2001?, Superior 2/02 - PCGS62
4) Simpson-Heritage 11/20 - PCGS63
Eckfeldt journal image courtesy of Alan Meghrig.