This is a well-executed copy of an Oak Tree Shilling, struck circa 1850-1860 by Thomas Wyatt of New York. Wyatt made a number of copies of various Colonial coins, the most famous of which is the 1652 Good Samaritan Shilling. The version being discussed here is known variously as Noe OA, Kenney 3, and Whitman 14040. All of these appear to be underweight, some grossly so, and all are below the expected weight of 72 grains (give or take) for a genuine Oak Tree Shilling. We have observed a range of weights from a low of 37.8 grains to a high of 69.2 grains. Presumably, Wyatt made these copies as options for collectors who could not afford the genuine articles. As good as the Wyatt copies are, they will not fool the knowledgable collector.
Wyatt copies are fairly popular and prices have advanced significantly in recent years (for instance a raw MS63 example sold for $1,175 in a November 2016 Stack's/Bowers sale.
At least two examples that we have seen of Kenney 3 show evidence of a double strike. Depending on the size of the planchet and the centering of the strike, some examples show a pair of raised, wavy, parallel lines on the right side of the reverse.