Some days it seems that no stone has been left unturned when it comes to the world of collector cars, but if you dig deep enough, there are still gems to be found. The W114/W115 Mercedes-Benzes, also known as the Strich Acht (or Stroke Eight) was not a particularly flashy or eye-catching vehicle, but this was the first post war Mercedes-Benz to use an all-new chassis. This car would last through 1976, when the W123 would carry the baton into the 1980s, making a name for itself around unmatched durability. In 1974, the OM617 inline-5 diesel would appear in the form of the 300D, an engine that would carry over to the W123 and even live on through 1991 in the G-Class. This 1975 300D for sale outside of Philadelphia has under 70,000 miles on the clock and certainly looks the part, ready to log another 70,000 miles in very short order.