I wonder if the glass and the clock were originally together? It seems odd that there is no easy access to the winding mechanism and that you would have to pull the clock out every time it needed winding. My understanding is Straub made the Mercedes branded clocks from about 1948 and into the 1980s. (I haunt watch and clock websites too.
Based on the clock IF the two pieces are original to each other I would place it in the '60s, give or take. Have seen what looked like the same clock movement in decorative mantle cases made many parts of the world. Hope that helps.