I have my great grandmothers 1900s singer sewing machine & would like to know how much it is valued for? The serial # is G14449Z6 and it's the 7 drawer Tiger oak model. It was purchased from MARV HELVIG, The Sewing Machine Doctor 1285 30th AVE NE, SALEM OR 97301. It works well & is in great condition. It also has the "STUDENTS MANUAL OF MACHINE SEWING . SINGER ." book #14 included. Could u please help me estimate its value?