RitekG05, strange issue

Hi peeps,

Like many of the NEC 35** owners… I 've been playing around with PIF/PIE checking the last days - at night.

Then I came across this horrible looking Ritek disc… which to my astonishment, can be read without many probs… not at full speed… but it reads (my nec 3520) it at 5 speed… no probs…

So now I wonder… how is it possible that disc disc can be read at ALL?
Someone with an idea?