The Look 585 series was the successor to the 381/481. The 481 replaced the 381 but they were nearly identical. This series came in about 14 different sizes, each one slightly optimized in its geometry.
The 585 had larger tubes, carbon lugs and used a standard sized seatpost, in contrast to the 481, which used a non-standard seatpost and aluminum lugs and dropouts. The 585 has much more carbon. It was also made in fewer sizes, either five or six instead of fourteen. Of great appeal to many people is the fact that Looks of this era use normal, threaded bottom brackets. Use your Shimano or Campagnolo or Sram with confidence. They are not proprietary.
I owned a 381 and really enjoyed it for several years but then graduated to a 585, which I felt never fit quite right. I own several today and feel the same way but they're within the margin of error and work just fine.
It's not clear to me why they have a nice ride quality but they are pretty good at muting and damping a coarse road surface. They're not overly stiff but are stiff enough for most riders most of the time
Things to watch out for, in my experience, are peeling clear coat and especially mismatched headset parts. I've seen this and getting the right washers and races is nearly impossible if the previous owner attempted to "Upgrade" their headset. Don't even try. They accept a standard bearing AFAIK but the races are critical.
The Origin and Ultra are identical AFAIK except the Ultra uses a different carbon layup and possibly an extra layer in places and is advertised as being 15% stiffer. This seems plausible as I've had both but I also think it may result in less damping of the ride quality. Again, it's splitting hairs and it can't be measured. I like the Ultra for the mental game that it's stiffer and also for the aesthetic of the black carbon.
They show up on eBay with regularity and the prices are reasonable. I would pay $800 for a real NOS version with fork and headset and up to $500 for one in excellent condition. But no more than this.
I also own a Giant TCR Advanced SL and the Looks get ridden more than the nominally "higher performance" Giant.
They're not super stiff but they're not noodles either if you're not a World Tour sprinter. They're fine road bikes if they fit your body shape and riding style. They are race bikes, not gravel bikes. I can fit 25mm tires on wide rims on mine but that doesn't leave much clearance. Mostly I use 23s on wide rims.
Hopefully this sheds some light on Look 585s. I think they were last produced about a decade ago, so honestly, they're no longer remotely current. But they are as good today as when they were produced and that was pretty good. Since I'm stuck in the past I'm OK with how they ride for my current mileage and riding style.
Here are the two in my fleet I ride the most. The white one lives in Minneapolis and gets ridden when i'm in town there. The black one lives with me in Chicago and gets the most mileage of all my bikes these days. Both are photographed at beer stops, which is how I enjoy my rides these days!
Look 585 Origin (repainted)
Look 585 Ultra
