Some of the issues have missing or partially missing overprints, doubled overprints and inverted overprinting. These were produced by overprinting Egyptian postal stationery. In addition to overprinting older issues, the government created new postage stamps. Such overprinting does not invalidate a stamp unless it shows through the front. Panama was billed for the cost of this overprinting. These were created by overprinting existing stocks of Netherlands New Guinea issues. Overprinting, as well as British counterfeiting, caused the value of the Continental to diminish quickly. Overprinting of a letter by the tilde was a working method of combining a letter.