I was hoping someone could tell me what type of revisions were added to Brittens' Clocks and Watches And Their Makers over the years and the various editions. I've seen the 7th 1956 edition around quite a bit and noticed that the 9th 1986 edition is much larger, but scarce. What was added over the years? I'm looking to buy a copy, but I'm not sure if I should just get the 1956 edition, or search around for the newest edition, or at least a newer edition than the 7th. Any opinions? Thanks all.