This is a review of the clock gallery only. As other reviewers have noted, this requires a separate ticket from the nearby treasure gallery.
This is worthwhile, but (on a weekend) it was extremely crowded. It is not large, but according to the website 82 clocks are on display. They are extremely ornate, and the workmanship involved is quite stunning.
If you can be there on a weekday, perhaps it would be less crowded and more enjoyable.