Nostalgia & History > SP identification markings help requested

Yesterday I picked up our latest velocipede addition from Tucson, Arizona. The velocipede is quite modern and looks identical to the closeup color image Evan posted on this thread:
http://www.trainorders.com/discussion/read.php?11,3539102

This afternoon Mason and I were able to strip away some paint to reveal some markings:

MWSP (pretty obvious what that means)

and

WO 10 14 55

I am going to assume the numbers represent the date. Does WO represents West Oakland? What did these markings signify? Is the date when the item was put into service? Does the "WO" represent where the item spent its career, or was this just where it began its duty? Did the railroad place an equipment inventory number somewhere on the piece to keep track of it?

Todd Clark
Canyon Country, CA
Trainorders.com