The Asus VC239H-W has a maximum contrast ratio of 80000000:1. That's over sixteen times the contrast ratio of the most common dynamic contrast ratio of 5000000:1. The best contrast ratio of all LCD screens of a similar spec and age to the VC239H-W is 100000000:1 and the worst is Mega Contrast.
We think you might also be interested in some of the alternative flatpanel monitors that have an 80000000:1 dynamic contrast ratio currently available including the Asus VX279Q (£197.39) which has a better Rating.
If the contrast ratio of this flatpanel monitor is too low for you then you might also want to consider the H277HU (£269.99) (100000000:1), or the G257HU (£228.57) (100000000:1) both from Acer which also has a higher rating.