I believe motorcycle dealer plates were introduced in the 1970s


                                                          1974                                                   1976



1990                                                     1991                                                     1997                                                       



                                2007                                                   2008                                                     2009 




Prior to 1991, dealer plates were denoted by an "L" prefix and used month and year stickers. 

After Jan. 1991 an "L" sticker was used with the month and year on one sticker.

The 1990 plate shown above doesn't fit either version. The Aug 1990 expiry on one sticker predates the Jan 1991 introduction of that sticker type and it also uses a PV sticker on the "L" series base.