There is a chart for the last serial number of each year here:
http://www.pianoworld.com/knabe.htm
http://www.pianoworld.com/knabe.htm arround 1913...
I have a Baldwin 621 piano with a different serial number and it was bought in 1988.
According to this.... http://www.bluebookofpianos.com/serial1.htm#WILLIS%20&%20SONS your piano was built (roughly) in 1910.
It should be around 1974. (For References see Related Links below)
According to my copy of the Pierce Piano Atlas, the Baldwin piano with serial number 127398 was manufactured in 1954.