Going with this minty Gruen "Precision Power-Date" today...circa early-mid 1960s...Gruen cal. 560 RSS was based upon a Bidlingmaier ebauche.
My 23-jewel Gruen Autowind calibre 629SS automatic of perhaps mid to late 1950s vintage. This one has a Durowe calibre 1162 movement in it. I believe your Bidlingmaier movement was of German manufacture (?). So is the Durowe of German manufacture. The case on mine is gold shell over stainless steel. Odd that an American company that used Swiss movements, used German movements on some models, I find.