I have put roughly 50 miles on them and purchased them "like new" from a triathlon wheel rental business in Canada.
Based on the fact that the wheels were only rented for events and I have put around 50 miles on them, I feel more than comfortable saying there are less than 1,000 miles on them.
They are in like new condition with no signs of wear. The brake track, free-hub, etc. All excellent condition.