Correct. 1997 W210s were not equipped with the Smart Key (DAS).
But they did have EIS (?), didn't they? Which is why a key copied at a locksmith won't work - the key won't have the required integrated chip.
Since the chip recognition system is apparently working (with the spare), all that should be required is renewal of the master key. Correct?
Or, have there been problems with the on-board chip recognition/start authorization system?