While it doesn't look like a YMCA logo in general, I can see how the right side can be flipped upside down to kind of look like part of the current Y logo and maybe get one thinking about it.

I think Duluth Area Vocational Technical Institute is the best guess so far. That's the name of what is now called Lake Superior College.

I have a hard time finding anything in that logo that resembles a T, but I still think it's likely to be correct.

Here's a rundown of Lake Superior College names throughout its history:

Salter School, 1946 to '68
Duluth Area Institute of Technology, 1968 to '72
Duluth Area Vocational Technical Institute, 1972 to '87
Duluth Technical Institute, 1987 to '89
Duluth Community College Center, 1989 to '95
Lake Superior College, 1995 to present

More on the history of the college at lsc.edu.