The Arms & Equipment in the Civil War Message Board

Civil War Sergeant Regiment

I have a tintype of a Civil War Union Sergeant that I'm trying identify. I've made a photograph under a microscope of the Sergeant’s kepi hat. The regiment number on the hat is very difficult to read, but is likely to be one of the following numbers: 75, 73, 33, 55, 35, 7 or 77. I'm trying to find someone who could tell me if any of these numbers would be more likely than others. I suspect the regiment is from New England. Can anyone help? Is there a specialist I should send the image to? Thanks. I have attached the image here.