Did you try using acetone? Typically logos printed on the lenses come right off. Just be careful you don't get it on the plastic frames. It might dull them. I would spot test on the lens too just to be safe.
I seem to remember starting on an old scrap "logo'd" test lens, first with WD-40, which didn't work, then acetone (Wife's nail polish remover) which I think either showed signs it was beginning to melt it or went cloudy - This might just be dependant on the type of plastic though, or maybe the acetone was of higher strength. Either way, I'm not 100% on this though, as it was a while ago.
In the end, I used a small amount of Autoglym polish with a soft cloth and it eventually took off the red Prada logo without scratching or clouding the lens.
(I found it again on p.108).
Cheers for the kind suggestion though, much appreciated.

I'll certainly give it another go at some point.
Acetone is in my DIY/crafts arsenal and worked in removing the black from my 2430s.