Both conditions must hold — only pick up iron plates that are also rare. Probably what most people picture, but it's not the only sane reading.
They're independent filters — pick up all iron plates (quality signal ignored/not applicable here), or pick up anything rare regardless of type ...

Add science cost option to signals output by labs (2.1)
Instead of only outputting 1 for a research requiring a science pack, it could instead output the current cost (such as 32k).


The change
Instead of only putting 1 on each required science pack as seen here: Current Output
It could ...