I am no expert on the D-9, but from what I understand from Deboeck et al.'s Vol. 2 on the Fw 190D markings and camouflage published by JAPO, this photo:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=180355825639
actually confirms that "<1-+-" was indeed W.Nr. 600150, as they speculate in said book, but were unable to confirm 100 % (see pages 302-306). Must be good to get that confirmation! Hopefully they will already have seen this interesting photo. If not, someone should notify them.
Kjetil