KE info, do you have the indicator lights?
i think the sticker for my 95 C-280 202 refers to both a car alarm and the stereo being coded. my car did not come with a KE system. this is the same as my prior 86 300e.
i think that the factory KE systems typically could be recognized by the inclusion of indicator "lights" on the front door handles and trunk.
there are several posts on KE systems on the boards. the one that might be particularly helpful can be found by searching using "the keyless entry guy". i think they were in the stereo forum.
i also want to add KE to my 202, but am inclined to probably go to an auto stereo shop and get a new alarm that includes the KE.
if you find that a DIY KE solution is really easy, i would appreciate any details you could share.