Units of paper quantity size and type of paper being sold. Reams of 500 sheets (20 quires of 25 sheets) were known in England in c1594; in 1706 a ream was defined as 20 quires, either 24 or 25 sheets to the quire. In 18th- and 19th-century Europe, the size of the ream varied widely. In Lombardy a ream of music paper was 450 or 480 sheets; in Britain, Holland and Germany a ream of 480 sheets was common; in the Veneto it was more frequently 500. Some paper manufacturers counted 546 sheets (21 quires of 26 sheets). J.S. Bach's manuscript paper at Weimar
Paper knife Paper knife The terms paper knife and letter opener are often used interchangeably to refer to a knife-like desktop tool. In truth, they are actually for different functions and were in use at different times. Paper knives are used for cutting open the pages of hand-produced books where the folding of printed sheets creates some closed edges that require severing of the paper. Letter openers "evolved" from paper knives into longer, blunter blades for the sole purpose of opening envelopes. Paper knives are no longer in common use, except perhaps by antiques enthusiasts. An electric version of a letter opener