i have several build plates for my K1 Max, all of them 2 sided covered wih PEI . i just assumed that the original black build plate with lettering on one side only has PEI on the printed side. i always use water resolvent spray glue and mistakenly used the unprinted side of the build plate and it worked out fine, i could get the printed part off after a couple of hours soaking in water.
That brings me to the question:
Does the original magnetic build plate have PEI on both sides?
I don’t believe so, because the PEI on the face is held onto the metal plate with adhesive. I ruined mine from accidentally letting the build plate slam into the hot end, and it scraped through the PEI “sticker”. I found your post while trying to see if I could replace the PEI coating sticker. If that’s possible, I would assume you could put one on both sides.