Need help identifying which channel balance to get

Hello there. Good eye. Because only the top fitting has wings and the bottom lacks them, I'd be inclined to say you have the S395-28. However, the Series 395 has a shoe that is 1-1/8" deep. See the diagram below for reference. Double-check the depth of your shoe. Since it's possible your old balance's shoe has worn from age, it might be good to check the other balance in the window, or from an identical window in the house. Let me know if this depth still does not match up. 

Assuming the S395-28 is correct, for a stamp option go with 2730. 

Close up view of the S395 balance shoe.

Hello again. So long as the bottom shoe is 1-1/8" deep, then the S395-28 is the balance you need. Let me clarify about the stamp option. The stamp option designates the strength of the channel balance--it is not a part number. In your case, go with 2730, which designates a balance that can support a window sash in the weight range of 13 through 19 pounds.

The photo in question unfortunately does not verify what Series you have. This only shows me the stamp, which we've already established as 2730.

Your next step needs to be to measure your shoe and compare it to the diagram I shared above. If it's the same size, then that's your top pick. If not, you need to tell me what size it actually is so that I can find you a better match.