The trade mark on the movement in the Gruen appears to belong the the firm H Becker. According to Mikrolisk, Becker was established as a watch case manufacturer in Pforzheim, Germany, in 1921. They began manufacturing watch movements in 1955. If these facts pertain to your Gruen, then it would appear as though it could have been made no earlier than the mid 1950s. As early as the 1940s, the majority of movements used in Gruen watches were made by Gruen, or Aegler. By the mid 1950s, Gruen sold out, and largely stopped manufacturing movements. Thereafter, movements from other manufacturers (Swiss & German) were used. Given the style of the Gruen, and the fact that Becker began manufacturing Watch movements in the mid 1950s, my guess is that your Gruen is more likely from the mid 1960s.
