Advance 5850

I recently purchased some vintage patterns.  I get really excited because it's kind of a grab bag type situation, I never really know what I'm going to get.  I thought this one was very cool for a few reasons.

First, it appears to be fairly rare.  I could only find one reference to it online and I couldn't find any for sale.  Secondly, it is almost in pristine condition.  There are two pieces that have been used, and are in great shape.  The others are still factory folded and instructions are complete.