Now you don't see one of these every day. Following some stiff competition from a certain party on eBay I acquired this eight years ago. Found in a barn on an old family farm in Norfolk, it had been in occasional use just about into the 21st. century. This one is post 1902 as it has the unusual Wansbrough Patent height adjuster. On the face of it this seems like a good idea and works well but one has to assume that the additional cost of manufacture is the reason why the idea did not come into more general and continued use.
Ironically, having trekked it all the way back home to the Surrey/ Hants border at the time, we subsequently moved to the Suffolk/Norfolk border, not that far from where it was.