We have a Grohe Geneva Roman tub set (25 506) and need to remove the lever handle (18 734). As best I can tell from the exploded diagrams shown in the Grohe documentation, there is supposed to be a screw (labelled "J") under the H/C button to hold the handle to the top of the cartridge. However, after unscrewing the button, I don't see any screw---just what appears to be a white annular disc divided into quadrants by grooves at the N, E, S, and W locations around the circumference. Through the center, I can see a brass fitting that I guess is the top of the cartridge. I've tried just lifting the handle, but, though it has a fair bit of play, it doesn't seem to pull off easily (and I didn't want to force it).

Does anyone on the forum know how to remove handles like these from a Grohe faucet or deck-mounted tub filler?

Thanks in advance.