What Does Letter-Quality Printer Mean?
A letter-quality printer is a type of impact printer where the printing element comes in direct contact with the paper, which gives a more professional look to the printed form. Letter-quality printers provide crisp and clear printing, similar to that of a printing press.
Techopedia Explains Letter-Quality Printer
Letter-quality printer was a classification given to some of the early impact printers that produced a cleanly printed document instead of the blotched and untidy output of some other types of printers. Letter quality simply means the quality of printing is similar to that of a professional printing press. These printers are now considered obsolete due to their large size, loud noise and inability to print graphics.
Non-impact printers such as laser and inkjet printers now give the same results as letter-quality printers with more convenience.