Postage Due - Plate Numbers

Pos Malaysia issued a set of postage due stamps on 15 September 1986 containing five denominations - 5c, 10c, 20c, 50c and $1. The stamps were printed without watermark. Later on, however, two denominations (10s and 20s) were reprinted in 1999 (according to SG catalogue). These reprints were SPM watermarked. I think the reprints in 1999 had plate number 1A (see the second image below) as that similar to the original print. Nevertheless, further reprints for 10c and 20c (also SPM watermarked) were produced most likely in 2004, and they can be identified by the plate number 2004/01 (see the first and third images below). The differences between the 1999 and 2004 reprints are quite clear (based on my observation on the 20c stamps). The colour of 2004 reprint is duller than that of the 1999, and the paper of the 2004 reprint is thicker than that of the 1999.