Four different reverse hubs were used in the 51 year run of the series. The first was the laurel wreath reverse of 1859(A), the other 3 were the oak wreath/shield combination from 1860 thru the end. The last 3 hubs are identified by their different styles of "N" in the denomination "ONE". The original Flat N of 1860 & 1861(B) was shallowed out in 1862(C) for better strikes in the hard copper-nickel. The final modification was the Bold N implemented by Charles Barber in 1870(D) after full strikes were no longer an issue in the softer bronze. Shallow and Bold N's can also be identified by their serifs (see arrows).