I finally bought from Jurgen Keller an HP27s.
Probably one of the best calculators ever made, second only to the HP42s and the HP15c when it comes to feature set and usability (should I say "third" instead?). It is a pity that it is not RPN. The menus are logically laid out, and it sports options like TVM that make it an excellent all-rounder. As well, it beats the HP42s in the time menu (I wonder why the 42s did not have 1. a better solver like this or the 17bII's and 2. A time menu. I remember 20 years ago, during my MBA, using it as a wake up call - there were no mobile telephones at that time (or the ones there were not really portable))