The post of the Escutcheon is peened over the "washer" and must be ground or filed to reduce the peened diameter to allow washer to slip off. Don't destroy the washer as it will be reused - at least in a proper installation. Some cheesy installs are just to glue in the replacement but that obviously is the easy and chessy way to go IMHO.
NOTE: I was referring to the Logo/Medallion at the top of the grip NOT the escutcheon that the grip screw goes into. I sometimes read the question too fast SORRY!
A Grip screw escutcheon can easily be removed by using the grip screw threaded into it to gently pull or push it out. They sometimes come out easily and sometimes require a bit of tapping, but do it gently! Make SURE you support the grip properly with some sort of block or you can also crack the grips. Just take your time and do not apply too much force or again the grips could crack.
When inserting the new one make sure you push it in evenly so it does not cock or go in slanted.