Well, I couldn't leave the problem alone! Believe that Bernina #1260 may be the first with a real blanket stitch. Prior, there was a stitch that
had a satin stitch with 2 stitches that would throw to the left. Very solid, but, combined with the satin stitch (even set very narrowly) would
probably not be what you are looking for.
I went to the berninausa.com site; on the left at the top is a link for 'support,' there you can find "out of print" manuals. Each will show the
stitches and functions. While the quality of the copy is not great, it is readable.
There is a 1260 currently listed on eBay: http://www.ebay.com/itm/Bernina-1260-Se ... 3f130ee329
Price at the moment is $399.99 US. This is close to what an 830 would
be offered at.
Hope this helps a tiny bit, I had fun!