Hard to say precisely to be honest. The company was founded in 1876, and this is the earliest design, as it appears in their original catalogue. They do a variety of sizes. Mine is a 405, if I remember correctly a 406 is smaller and a 404 is bigger in terms of the size balance wheels they are intended for. Each design is double ended so can accommodate larger wheels at one end, smaller at the other. This one fits your typical pocket watch balances perfectly.
The design changed subtly over the years, a friend has one with the original paperwork dated 1888 and his is slightly different and seems to be a later type. I have also seen one with a definite date of 1906, which is different again. It hasn't got a patent number on it which might be helpful although that of course can only give you a "must be later than date". None of the old ones I have seen have any reference to a patent. Later ones have "patented" engraved on the tool, and printed on the box but no numbers.
So I suppose we could say late 1870's to mid 1880's to be more precise? I think the guy I bought it from advertised it just as 19th century, which is pretty safe. I can't say I have ever really looked into it, beyond a quick Google.
Kendrick and Davis carried on making watchmaking tools well into the 20th century, and was wound up in the 1990's, although I think they were doing other things by then.
I just love these old watchmaking tools, beautifully made, and very cheap compared to their modern alternatives. I think I paid about £50 for it, and it is complete with the little bar tool for tweaking the wheel back into shape, not in the photo. These usually get lost. A modern one of comparable quality is far more. I bought it as a functional tool rather than an antique, and use it regularly,
Always happy to know more though. What was it about the box that makes you think it is later?