The numbers stamped on the plate that you are referring to, are with regards to the pendulum and beat rate. The clock is made for a 15 cm drop measured from the top of the suspension spring to the center of the bob. The 178.28 is a beat rate. This should be a beat per hour as 178.28 beats per minute would be quite fast. As far as age of the clock goes, there is really no good way to tell how old the clock is other than model number and possibly a letter that is sometimes stamped on the plate. Try to do an internet search on the model number of the hermle. The suffix on the part number may also help to narrow down the age of the movement. Welcome to clock repair. I hope you have many rewarding hours of repair work.
.
