extent

a census or valuation of all the lands in Scotland for tax purposes.  The ‘auld (old) extent’ was probably made in the 13th century.  Under the Act 1474 it was replaced by the ‘new extent’ (which was often just the auld extent multiplied by 4,5 or 6).  Lands continued to be described in terms of these extents long after either were made as e.g. ‘the ten-shilling lands of ….. of auld extent’