My 250 assorted screws arrived today. As I had a gander at them through a loupe I noticed that quite few were rusted, some badly.
I picked out any that were at all corroded and found a total of 28. Out of 250 screws that's about 11% rejects, however I thought I'd count them and sort them as they were all mixed together.
In the end I counted a total, including duff ones, of 362 screws! I don't think I can complain too much in this case as the good ones worked out at about tuppence a screw!