Hope nobody minds my posting this link here, but I've put a 1987 service manual (Chassis and Body) for the Series 123 Mercedes-Benz on eBay. The chapters cover Electrical Equipment and Instruments, Windows, Interior Equipment, Doors, Trunk Lid and Exterior Flaps, Sliding Roof, Central Locking System, Electrical System of Body, Detachable Body Components and Seats and Seat Belts.
The auction ends January 8th, and there's no reserve, and since there aren't any bids on it yet, it's likely you'll get it if you bid.
Please take a look at the auction if you're interested at:
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Thanks!