The following is an undated letter by James Longacre in the Library Company of Philadelphia (box 3, folder 6) apparently about the 1856 flying eagle cent.
The new (or experimental) cent"
"This coin differs very materially from any before issued from the Mint: In quality of the material, in relative proportion of diameter and thickness, and in the device:
1) The material is a mixed metal harder and of a lighter colour than copper and liable to oxidize or tarnish in using: while strikingly different from either the gold or silver coin in appearance.
2) The relative proportions of the piece, are most obviously varied from the other coins retaining as it does, very nearly the thickness of the old copper cent, while the diameter is very slightly (one twentieth of an inch) over that of the dime: this peculiarity of proportion is relied upon as one of the greatest safeguards against mistaking it for any coin of greater value amonth the precious metals.
3) The greatest novelty presented by the device amongst the other coins is that of the Flying Eagle on the obverse: opinions will doubtless vary as to the propriety of this design so far as the quick and ready distinction of a coin by its device is a desideratum, we think the object is very effectually accomplished by this device: the merits of its heraldic or artistic applicability, might lead to a more extended discussion, than it is any part of our present purpose to invite. The reverse is simply a wreath encircling the denomination - the propriety simplicity and beauty of this arrangement, needs only to be observed to mark it as one of the most perfect amongst our coinage. The wreath it is true, is similar in design to that of the Three Dollar gold coin; but the greater thickness of the piece enabled it to be brought out in higher and more perfect relief: besides filling more completely the face of the coin.