ARF it´s the ¨name¨ of the factory. Probably A. and R. are the inicial letters from the first, last names of the founder. This is something recent from these latest two years when suddenly so many factories made same/similar models, that somehow we have to distinguish them and in the beginning was v1, v2, v3, but the orders were quite misleading as the latest v was not necessarily the best, and each month there was a new v, there were factories which were already had a kind of name or nickname, for example the Noob factory, which got the name from making beginner or noob watches formerly, than they started the top quality ones, and now we have these similar sounding ¨names¨ which are strange to us, but at least easier to distinguish
Currently there are about 25 high end factories and not sure who makes up their names...
I am sure no one uses chrono, because it´s more like a decoration, even for the gen, it´s like the 5th button up on your blazer, it´s there, but you never use it