Horolovar 400 Day Clock Repair Guide, 10th Edition, written by the late Charles Terwilliger, and edited by H.W. Ellison. Copyright 1991, Hardcover, 237 pages. ISBN: 0-916316-04-1

This is the latest edition, with 50 new back plate illustrations, other new material, and many other updates from the 9th edition. Known as the bible of anniversary clocks, this fascinating and comprehensive book is a must have reference for serious collectors, horologists, and indeed anyone with an interest in these beautiful timepieces. Divided into 18 sections, features include:

• The history of 400 day anniversary clocks
• Patent informaion
• Hundreds of photos of clocks and pendulums
• A detailed study of escapements
• Troubleshooting and repair tips
• Back plate illustrations to identify manufacturers and manufacture dates
• Technical specifications for mainsprings, suspension springs, and suspension units
• Chart linking manufacturers and importers
• Illustrated movement parts lists for major post WWII manufacturers
• Loads of interesting 400 day anniversary clock trivia