Hard to say... so many people did bodies on these things, and the ones from the factory where pretty much all customs. Your going to need to find a picture of pretty much the exact same car and match it up, or someone will have to be a specialist in prewar German cars to ID it. There are some things that make me think it is a later car from the early 30's though... The vent integration into the hood does point to in house Mercedes circa 1930, it could be a w08 mercedes.
https://translate.google.com/translate?hl=en&sl=de&tl=en&u=https://de.wikipedia.org/wiki/Mercedes-Benz_W_08 as already noted
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