I have looking at this model for a while but cannot bring myself to buy one yet
The first series with sunken sundials are the most desirable and most expensive
As to wether this is worth it is a personal decision
Series 2/3/4 have small but significant differences but pricing is much the same with series 2 being the most expensive
If you buy try get one with all original papers and winding box
Make sure the later series have both case backs
Good luck
Jukian