Can you elaborate on how this works and what kind of screens the 2x3 screens are? 
Im picturing that you sorta press and roll the bud between the card and the screens and the seeds stay on top of the screen while the bud remnants fall through the screen?
I actually use my trim bin now, but the same thing applies. I tilt the screen slightly so the top is higher than the bottom. Break up the buds at the top of the screen and the seeds roll to the bottom while the plant matter stays at the top.
Oh ok, so the plant matter like “sticks” to the screen? What kind of screens do you use if you happen to remember
Any silkscreen will do, I use a 110 LPI screen. You can collect the kief from under when done too.
The same principle would work on any hard surface really. Got an old LP album? 
Round seeds roll.
I dry my trimmed seeded buds out fully. Place the Buds in a bucket with lid and shake aggressively. This usually releases 90% of the seeds from the dried bud.
Any seeds remaining get plucked from the Buds as I smoke them.