Marshall's lighter-man's best assistant, or, Coal-dealer's guide [electronic resource] : containing tables, exactly calculated for the ready finding out the true value of any quantity of coals, from 1 to 400 chaldrons, from 19£ per score to 40£ per score, reckoning 21 chaldrons to the score, including the metage-money : together with two tables, one of 25£, the other of 40£ per score, without the metage : the whole (having full explanations of the use of the several tables) is very necessary for lighter-men, coal-merchants, and all gentlemen who have any occasion to buy or sell large quantities of coals