Q1. Here comes the 'I know nothing about classic cars' question: to start this car, is it just a case of sticking in the key and turning it, the same way a modern car starts?
Q1a. Does a key look like a regular key?
Q2. Would one of the larger models (this page talks about six-seaters) be likely to have jump seats of any kind?
Googled: phrases combining the words Mercedes, Mercedes Benz, 1940s, classic, vintage, ignition, key(s), Grosser, jump seats. ('Nazi cars' was predictably unhelpful....)