Nothing for sale at the moment ;-)
The nut (and the rest of the aluminium parts) are 7000 series aluminium, and should be strong and robust. However 7000 series alloy can be quite corrosion prone if not protected by anodising.
I have seen some "copies" made in 6063 (the old BS. HE9), which is more ductile, and good for formed parts, less so for machined parts. Could be these you've seen. I also don't know of the alloy of the Bici/ Ofmega clones that are out there either.
The nut (and the rest of the aluminium parts) are 7000 series aluminium, and should be strong and robust. However 7000 series alloy can be quite corrosion prone if not protected by anodising.
I have seen some "copies" made in 6063 (the old BS. HE9), which is more ductile, and good for formed parts, less so for machined parts. Could be these you've seen. I also don't know of the alloy of the Bici/ Ofmega clones that are out there either.