Since Mercedes had a company policy of making changes when they were able to find something that worked better than before they would just make changes as the years went by. Hence there was no 'year'. There was the model.

This was no big deal in most of the world but it was in the US. And that's where things get weird.

Dealers found that selling 'last year's car' was a problem. They could not move them without a discount which the factory would not give. So, with a bit of pencil whipping, a last year's car magically turned into a current year's car.

I bought a 111 once that was presented as a 1962. But all the paperwork inside it, like repair orders, listed it as a 1964. The title said 1962. In the end I didn't really care since the only ones who would care would be a bank and that would only be if they were loaning money on it.

You can sometimes tell by the last numbers of the VIN but even that's no real help since sometimes Mercedes started over.

When buying parts the big deal is the VIN. When buying parts with a part number on them the big deal is the part number since over the past 50 years or so a previous owner might have found something that worked that was not original equipment.

So the year might be interesting to know but it is not vital to buying parts.