| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Definition:  An identifying number assigned to the product of one melting in an electric arc furnace: e.g. 19345. Sometimes, but not universally, the first digit indicates the furnace number; the second digit indicates the year in which the heat was melted. The last three (and sometimes four) digits show that this was the 345th heat melted in No. 1 furnace during 1989.