Well done Mattia for getting these 03 card standoffs sorted.
I think the original SSL versions were some sort of medium / hard nylon versions in (nearly) white natural colour. They could take a M3 x 6mm pozi pan screw which would cut it's own thread (the original hole diameter is so important for this ... too much and it became loose and too small, it could break it).
The balance was to have the right material which could be self tapping and still take multiple fixings over time. In my experience, I have never known one of the original ones to fail (PS: they were never meant for 4.40 screws ... 6 BA maybe but not 4.40!). Hope this helps somewhat.