I traded for a small quantity of Silver Blues a while back and have used one for my last 2 shaves after your post reminded me I had some and that my early impression was that it was a very good and a very sharp blade.
After these last (2) shaves, I believe it's the sharpest non-Feather blade I've used for several weeks. Maybe months. That includes Personna Meds and Labs, Super Iridium, Polsilver, and Astra SP. For me it's still not as sharp as the Feather.
The other blade that I tried a while back that I thought was approaching Feather sharpness was the Gillette Bleue Extra (NOS). I haven't used one recently however.
The Gillette Bleue Extra is still sold at online stores in France. I am not sure what the deal is there, but prices are between 2 and 3 Euro for ten packs. I have seen them sold in 12 blade packs as well (strange packaging). Maybe they're not the original NOS blades if you were referring to the ones that used to be manufactured in France. Google.fr ... "".