The post office had become so efficient by 1851 that Congress was able to reduce the common rate to three cents (which remained unchanged for over thirty years), necessitating a new issue of stamps. Moreover, the common rate now applied to letters carried up to 3000 miles. This rate, however, only applied to prepaid mail: a letter sent without a stamp still cost the recipient five cents—clear evidence that Congress envisioned making stamp use mandatory in the future (it did so in 1855). The 1-cent drop-letter rate was also restored, and Post Office plans did not at first include a stamp for it; later, however, an essay for a 6-cent Franklin double-weight stamp was converted into a drop-letter value. Along with this 1¢ stamp, the post office initially issued only two additional denominations in the series of 1851: 3¢ and 12¢, the three stamps going on sale that July and August. Since the 1847 stamps no longer conformed to any postal rate, they were declared invalid after short period during which the public could exchange old stamps for new ones. Ironically, however, within a few years the Post Office found that stamps in the old denominations were needed after all, and so, added a 10¢ value to the series in 1855, followed by a 5¢ stamp the following year. The full series included a 1¢ profile of Franklin in blue, a 3¢ profile of Washington in red brown, a 5¢ portrait of Thomas Jefferson, and portraits of Washington for 10¢ green and 12¢ black values. The 1¢ stamp achieved notoriety, at least among philatelists, because production problems (the stamp design was too tall for the space provided) led to a welter of plate modifications done in piecemeal fashion, and there are no fewer than seven major varieties, ranging in price from $100 to $200,000 (the latter for the only stamp of the 200 images on the first plate that displays the design's top and bottom ornamentation complete). Sharp-eyed collectors periodically find the rare types going unrecognized.