In trading on Friday, shares of the British Pound Sterling Trust ETF ( FXB) entered into oversold territory, changing hands as low as $153.215 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of British Pound Sterling Trust, the RSI reading has hit 29.6 — by comparison, the RSI reading for the S&P 500 is currently 66.1. A bullish investor could look at FXB's 29.6 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), FXB's low point in its 52 week range is $153.215 per share, with $169.06 as the 52 week high point — that compares with a last trade of $153.61. British Pound Sterling Trust shares are currently trading down about 0.5% on the day.