German Tank Problem – Passion is like genius; a miracle.

http://en.wikipedia.org/wiki/German_tank_problem

How to estimate # of products from observed serial numbers. Let $k$ be the number of samples and $m$ be the maximum serial number. Then, $\hat{N} = m + m/k - 1$ . Because $m$ underestimates $N$ , we compensate it by adding the number of missing samples between adjacent observed samples. Also, -1 because we don’t count sample itself when considering missing samples.

Given that, here’s a story on estimating the # of XBox: Xbox Serial Number Statistics