The serial # is 3205025 (it doesn't have a letter) and If i'm reading the singer website correctly that means it was issued that number in 1879. But the throat plate says patented usa aug 2nd 92.
serial at base of piller on the back
[ATTACH=CONFIG]90622[/ATTACH]
throat plate
[ATTACH=CONFIG]90776[/ATTACH]
better pic of the end
[ATTACH=CONFIG]91010[/ATTACH]