some of them are still in production. Sir William Hamilton's collection of ancient Greek vases was an important influence on Flaxman's work. These vases were first known in England from D'Hancarville's engravings, published from 1766. Inspiration for Flaxman and Wedgwood came not only from ancient ceramics, but also from cameo glass, particularly the Portland Vase which was brought to England by Sir William Hamilton by 1784. The vase was lent to Wedgwood by the third Duke of Portland from 1786. Wedgwood devoted four years of painstaking trials at duplicating the vase in black and white jasperware, which was finally completely in 1790, the figures perhaps modelled by William Hackwood. The replica was exhibited in London in that year, with the initial showing restricted to 1,900 tickets, which soon sold out. Wedgwood's careful copies proved extremely useful when the vase was smashed in the British Museum in 1845, and then reconstructed by the restorer John Doubleday. The original edition was of 50 copies; in 1838 a further edition was cast in one piece, with the background then painted. Date markings Wedgwood jasperware can often be dated by the style of potter's marks, although there are exceptions to the rules: Before 1860: Mark is "Wedgwood". Usually accompanied by other potter markings and a single letter. From 1860 to 1929: A three-letter mark represents in order, the month, the potter, and the year. The year code starts mid-alphabet with the letter "O" for 1860, the letter "P" for 1861, etc., returning to "A" after "Z". For certain letters there are two possible year dates. Unfortunately these date codes were used quite infrequently on jasperware pieces. A single letter is more commonly found during this time period but it is merely a potter's mark and of no consequence for dating the object. 1891–1908: Marks are "Wedgwood", "England", separated. 1908–1969: Marks are "Wedgwood", "Made in England", separated, or "Wedgwood England" on small objects like thimbles. After 1929 the typeface of the word "Wedgwood" is changed to sans serif. 1970–present: Mark is "Wedgwood Made in England" as single stamp Other jasperware Jasperware was widely copied in England and elsewhere from its introduction, especially by other makers of Staffordshire pottery. The Real Fabrica del Buen Retiro in Madrid produced jasperware effects in biscuit porcelain. At the end of the eighteenth century they made jasperware plaques for a "porcelain room" in the Casita del Príncipe at the Escorial.