I used a down one like that (a few years older) on a 35 day trip in the AK Range and froze my ass off, even with puffy coat, heavy fleece(s), poly pro liner, bivy sack, down booties, and all the poly pro layers I had (light, med & heavy) in an exp tent.  However, we saw temps in the -40 to -50F below zero (April).  My  buddy had a Marmot CWM -40 and was comfy the whole trip. I'd add +20 to the rating for "comfort".  You would likely survive at it's rated temp.  Also, if it has been used a lot or not stored properly over the last decade, it could well have a lot less loft, especially if it is down...