Just guessing here......Looks like it could have been made by Actron ..the later home of Sun/Sunpro .. This is a local, Cleveland, based company that may of had ties to Mr. G....A lot of the early Mr.G stuff was made here in Cleveland and then repackaged as Mr.G...The redine adjustment dial and pointer definatly look like a Sun product....The font and colors look a bit "cheaper"..more of a "knock off" line ..I believe Actron aquired Sunpro in the late 1980's.However the Mr.G logo and redline adjustment dial appear to be of a much much eariler vintage....
Steve