I believe this is a Federal Staff Officer's button.  And with that backmark, it IS 1850-1865.  It's a "muffin-style" button.
I'll see what else I can turn up...
-Buckleboy
Spring 2012 CaneField Bandits Totals: TEN Half Reales:
1740, 1777, 1784, 1796, 1801, 180?, 1806, 1807, 1808, and 1814
1836 8 Reales
A 17?? One Real
1819 Token/Jeton
Two "Russian Blue" Trade Beads
Henry Clay Campaign Button, 1820s or 1830s FIVE Early New Orleans Seated Coins:
1838-O Dime (no stars), Two 1839-O Half Dimes, an 1840-O Dime, and an 1842-O Half Dime
1892 Barber Dime
1918 Walking Liberty Half
1866 and 18?? Shield Nickels, and some GawGag V's and Beefaloes. Military Relics: Possible Spanish Colonial Era Cap Badge
FOUR War of 1812 Artillery Buttons
1820s Pewter Militia "U.S." Button
CW Eagle Artillery Cuff Button
CW Eagle Infantry Officer's Coat Button
3-Ringers, Enfields, Musketballs, and Shell Fragments
Any relics, coins, or other items appearing in my finds posts were found on PRIVATE PROPERTY with total consent and permission from the owners of said property.
Can I see a photo of the button "head-on" in order to see how much gilding is left?
I'd say that even without the shank this is still a $30-$40 find.  
-Buckles
Spring 2012 CaneField Bandits Totals: TEN Half Reales:
1740, 1777, 1784, 1796, 1801, 180?, 1806, 1807, 1808, and 1814
1836 8 Reales
A 17?? One Real
1819 Token/Jeton
Two "Russian Blue" Trade Beads
Henry Clay Campaign Button, 1820s or 1830s FIVE Early New Orleans Seated Coins:
1838-O Dime (no stars), Two 1839-O Half Dimes, an 1840-O Dime, and an 1842-O Half Dime
1892 Barber Dime
1918 Walking Liberty Half
1866 and 18?? Shield Nickels, and some GawGag V's and Beefaloes. Military Relics: Possible Spanish Colonial Era Cap Badge
FOUR War of 1812 Artillery Buttons
1820s Pewter Militia "U.S." Button
CW Eagle Artillery Cuff Button
CW Eagle Infantry Officer's Coat Button
3-Ringers, Enfields, Musketballs, and Shell Fragments
Any relics, coins, or other items appearing in my finds posts were found on PRIVATE PROPERTY with total consent and permission from the owners of said property.
With the "push" in the center, I'd put it in the lower range of what I said above, but it is still a Very attractive button.  Staff Officers Buttons are pretty difficult to find compared to the usual two-piece eagles.
Congratulations!
-Buckles
Spring 2012 CaneField Bandits Totals: TEN Half Reales:
1740, 1777, 1784, 1796, 1801, 180?, 1806, 1807, 1808, and 1814
1836 8 Reales
A 17?? One Real
1819 Token/Jeton
Two "Russian Blue" Trade Beads
Henry Clay Campaign Button, 1820s or 1830s FIVE Early New Orleans Seated Coins:
1838-O Dime (no stars), Two 1839-O Half Dimes, an 1840-O Dime, and an 1842-O Half Dime
1892 Barber Dime
1918 Walking Liberty Half
1866 and 18?? Shield Nickels, and some GawGag V's and Beefaloes. Military Relics: Possible Spanish Colonial Era Cap Badge
FOUR War of 1812 Artillery Buttons
1820s Pewter Militia "U.S." Button
CW Eagle Artillery Cuff Button
CW Eagle Infantry Officer's Coat Button
3-Ringers, Enfields, Musketballs, and Shell Fragments
Any relics, coins, or other items appearing in my finds posts were found on PRIVATE PROPERTY with total consent and permission from the owners of said property.
I should've known not to make any value estimates on this site. But I have just looked at several online with values in the range I listed above.
Either way, my ID was correct.
Now get out there and make some more GREAT finds.
-Buckles
Spring 2012 CaneField Bandits Totals: TEN Half Reales:
1740, 1777, 1784, 1796, 1801, 180?, 1806, 1807, 1808, and 1814
1836 8 Reales
A 17?? One Real
1819 Token/Jeton
Two "Russian Blue" Trade Beads
Henry Clay Campaign Button, 1820s or 1830s FIVE Early New Orleans Seated Coins:
1838-O Dime (no stars), Two 1839-O Half Dimes, an 1840-O Dime, and an 1842-O Half Dime
1892 Barber Dime
1918 Walking Liberty Half
1866 and 18?? Shield Nickels, and some GawGag V's and Beefaloes. Military Relics: Possible Spanish Colonial Era Cap Badge
FOUR War of 1812 Artillery Buttons
1820s Pewter Militia "U.S." Button
CW Eagle Artillery Cuff Button
CW Eagle Infantry Officer's Coat Button
3-Ringers, Enfields, Musketballs, and Shell Fragments
Any relics, coins, or other items appearing in my finds posts were found on PRIVATE PROPERTY with total consent and permission from the owners of said property.