Welcome to the forum , karima .
From your post , it sounds like the upper end (value-wise) is that you've loved these lamps for a long time .
Sometimes the real value of an item from a familys' inheiritance is in our emotional attachment to it .
I hope you get to enjoy yours for a lifetime !
I'm no Benrose expert , so I don't have any info I can pull out of my hat for you .
We'll see if other members have got some Benrose-savvy .