I just picked up a 4566 recently and was wondering about it. From searches on here and other sights I am inclined to think it was an early example. It has (totally dead) Trijicon sights which show a date of 96 on the rear sight, I realize this might not be the year that the pistol was made. It has no lightening cut above the trigger, the trigger guard is square,the hammer and trigger are stainless and there is no ridge along the top. The serial number is TEZ49XX. I don't own the book that I have seen mentioned in determining production date, any help would be appreciated. I had a 645 back when they were new and always regretted selling it, but I think I like this one even better.