Always keep a mouthpiece in original condition if you intend to sell it. Photograph it carefully up close, describe it accurately and put it on ebay. Someone somewhere is looking for what you have. If it is altered, a rare piece is gone forever. Recovering the cost of refacing is difficult or impossible, and usually the value declines dramatically.
Not everyone is looking for a big facing, and even those who are usually want to choose the one who does the work.