So I tried twisting hard on defroster element to remove but no luck. May be force is not enough, can i tried moving locks with flat head or something or that may be risky.
Or there is some other trick. I guest its second generation based on 83-665.pdf

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1) '04 S500 Gold/Beige......120k Miles
2) '93 300E 2.8...Green/Tan MBTex..........202k Miles(and going)
3) '89 420SEL...Light Blue/gray Leather....155k Miles (Retired )