1. What was the earliest successfully designed and manufactured chronometer watch? is it in any museum or in private collection? 2. How many Harrison's H4 and H5 were produced in total? is any of these masterpieces in the market? 3. what was the earliest successfully designed and mass-produced chronometer watch? are they collectible and affordable? 4. How many chronometer watches are considered historically important? How and why they are important? 5. How many types of escapements were used on those historically important watches? which one is the most commonly-seen among them? 6. If I start being interested in early chronometer watches(before the mass-production period), which one you would recommend me to study, purchase and collect?