And a google search for this CUSIP 63861CAD1 shows only one page in cache for an ETF that added this ticker, but if you open the page they have removed it again:
Really strange why Nationstar issues new bonds having a WAMU ticker...
I mean, the CUSIP is relevant, but WHO assigns the ticker?!?
EDIT:
Probably a plausible explanation: All WMI debt was assigned WAMUxxxx, and since COOP basically is reorganized WMI, and nobody changed that, all COOP debt gets a ticker WAMUxxxxx assigned?!?