I just had the fortune to purchase a 1975 bronze pair of totally original Quad ESLs, from the son of a man who had hung on to them for life. He was going through some lean times and hated to sell them. I paid what he asked, and told him "Hats off to your father."
They are not even dusty. The grills are perfect, and are beautiful, with fascinatingly varied colors and textures in different lighting.
They charge up astonishingly quickly. My '81 black pair takes days to have good treble, and will be overhauled. (Kinda like motorcycles - gotta have a spare for when one is in the shop ;)
His father's (brother?) had bought three pair new in England and given him one pair. He only played classical music, at moderate volume. After I got them home, I found them set for 240 volts, perhaps running all that time - 38 years - at half charge. Talk about babied !!
They will pass on to a new owner when I pass on myself, hopefully after many, many happy hours of listening...