The other notable artist of this period is known as the Housebook Master. He was a highly talented German artist who is also known from drawings, especially the Housebook album from which he takes his name. His prints were made exclusively in drypoint, scratching his lines on the plate to leave a much shallower line than an engraver's burin would produce; he may have invented this technique. Consequently, only a few impressions could be produced from each plate—perhaps about twenty—although some plates were reworked to prolong their life. Despite this limitation, his prints were clearly widely circulated, as many copies of them exist by other printmakers. This is highly typical of admired prints in all media until at least 1520; there was no enforceable concept of anything like copyright. Many of the Housebook Master's print compositions are only known from copies, as none of the presumed originals have survived — a very high proportion of his original prints are only known from a single impression. The largest collection of his prints is at Amsterdam; these were probably kept as a collection, perhaps by the artist himself, from around the time of their creation.