I saw one of these plates the other day. It was located on the radiator support, just to the right of the hood latch if you are standing in front of the car and looking back at it.

A very unimpressive looking thing, just a flat piece of metal with some numbers stamped into it. But the bottom line was the VIN. It did not identify it as such, but that's what it was.

This was on a 1966 230, which is a W110.

It was also painted body color, but this could be where a repair was done and it was just sprayed over. A lot can change in 47 years.