| Year | Value | Month | Value |
| 1975 | F | January | 1 |
| 1976 | H | February | 2 |
| 1977 | I (J) | March | 3 |
| 1978 | K | April | 4 |
| 1979 | L | May | 5 |
| 1980 | M | June | 6 |
| 1981 | N | July | 7 |
| 1982 | P | August | 8 |
| 1983 | R | September | 9 |
| 1984 | S | October | 0 |
| 1985 | T | November | N |
| 1986 | U | December | D |
| 1987 | V |
"UB880D WD MME" was made in December 1988 |
|
| 1988 | W | ||
| 1989 | X | ||
| 1990 | A | ||
| 1991 | B | ||