The W115's are a totally different style. The brand name used on the 115's was Kangol, and their two parts were hooked together kinda like two hands after the fingers have been curled. There is also a small magnet to keep things aligned I believe. Unlike the 123's, there is no release button as such. To open the Kangol, one half of the unit is levered away from the other mating part. Quite different.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150