I just picked up one of the 585-1 models, #143/250, and since the stock 585 is my very favorite sub 3" knife this one with G-10 scales makes the knife what it truly should have been all along.
Nothing really wrong with the Valox scales, but the G-10 makes the knife shine, and the added benefit is not only the look and feel, but the added grippiness from the textured scales.
Rx is correct in what he said above, and FYI the prototype of the 580, the larger version, did come out in G-10 and was switched to the Valox in the full production run. I don't know if the 585 prototype came in G-10 or not.
Here's photos of the 585 Valox on top and the 585-1 G-10 below:
And while I'm at it, here's photos of the larger 580 in Valox and the prototype in G-10:
BTW - last time I checked, the KnifeWorks had the 585-1's in stock...!