Any help figuring out the story on this clock? Back is stamped Lenzkirch, and has "396" near the logo. Also has a handwritten number "4388" on the back. Has a "SONOSONG" movement/chime. My Father was a pilot in the USAF and had rotations into Germany in the 1960s, where he purchased this clock. It was in my bedroom growing up, and now it's in the living room of my home. Where is the serial number located on these clocks?