It's an old model, at the bottom end of LG's support pile. Having sat in its box for 4 years, and not knowing how it's been stored, it's a bit of a gamble to my mind. I wouldn't offer anything more than £250, £300 tops.
Agree with @Clem_Dye here.. Its a big gamble dispite it being stored away for 4 years.
It will either go 2 ways you will have a perfect fully functioning E6 that will hopefully last you for a good few years without fault... Or... You will be riddled with the ussal OLED faults that folks still get with recent models.
Obviously their is absolutely no software /firmware surport for this model. Those E6 panals are way long out of service produced and even the main boards you would have to source 2nd hand on ebay for repair.
So yeah it's a big gamble I certainly would not pay more than £350 top wack if you have that type of cash to depose of or maybe you know someone as an TV engineer with a workshop a friend or some sort that can help you out if things go wrong.
Anyways all the best with that.. The 2017 Range was far better in terms of quality to be honest that's were LG was gainig serious ground with their OLED lineups. But not to say the 2016 wernt bad.