The rear suspension of the W114/W115 was the pattern for the W123, W116, W126 and R107 rear suspensions.

Typical was the stamped steel trailing arm which mounted to the subframe and held the rear wheel bearing and the brake.

There were several w126 models that discarded the stamped steel trailing arm for a cast or forged magnesium unit, the 500SEL and 560SEL are two cars I've seen so equipped.

Your second picture looks like it might have one of these cast arms in place of the expected stamped steel.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles