Okay, now for a rundown on the Typ 300 family which includes the W186, W188 and W189.
The W186 was built between 1951 and 1957 and was a 3.0 litre 6 cylinder (sidenote: this engine in fuel injected form (and with some other performance upgrades) was used in the 300SL gullwing and roadster). The models offered on the W186 platform were the 300, 300b and 300c. The body styles offered were sedan and cabriolet.
The W188 (series 1) was built between 1951 and 1958. It was offered as a 2+2 coupe and cabriolet as a 300S. It was the most expensive of the Typ 300 family.
The W188 (series 2) saw the adoption of the low-pivot IRS and fuel injection. It was offered as a two door coupe or cabriolet/roadster 300Sc.
The W189 was the final member of the Typ 300 family. It was offered as a four door sedan and cabriolet, and came without the B-pillar... in effect it was a four door coupe or cabriolet. The only model offered was the 300d.
Pic 1 is a W186 cabriolet
Pic 2 is a W186 coupe
Pic 3 is a W188 (series one) cabriolet 300S
Pic 4 is a W188 (series one) coupe 300S
Pic 5 is a W188 (series two) cabriolet 300Sc
Pic 6 is a W188 (series two) coupe 300Sc
Pic 7 is a W189 four door cabriolet 300d
Pic 8 is W189 four door pillarless coupe/sedan 300d NB. This is the car Ash has spotted... you may have to change the thread title. Sorry... my memory wasn't as good as I thought it was.