From 1982 to 2001, Cambodia had most of her postage stamps designed and printed by COPREFIL, and to make more philatelic sales, all of these stamps have a certain quantity cancelled-to-order (CTO). Just as all other modern CTO, negative stereotypes and heavy generalization has made Cambodian CTO nothing more than gap fillers.
Personally I do not reject CTO. As a matter of fact, some modern CTO are so sought after that they fetch hundreds of US dollars. Although Cambodian CTO mostly end up in value packs for starters, with a closer look they do have little interesting information for collectors.
The Cuban printer sometimes included print run information on philatelic pamphlets, but it seems that the numbers do not include CTO quantity. Extra number of stamps were printed and then machine postmarked, this cancellation was not printed along with the stamp design.
Not all stamp printing sheets have serial number, but CTO are always on non-numbered sheets.
The machine postmark design has been revised a number of times during the two decades of CTO flourish, however only the very first one is identical to the handstamp postmark used in the Cambodian post offices, all others are nothing close. This makes collectors easy to tell CTO from postal used stamps.
The Date shown on cancellation is not first day, sometimes a week after, sometimes longer, yet it does not go further than a month. The following is a first day cover and a CTO of the 1993 BRASILIANA'93 S/S, note the cancellation and date difference:
It is very rare that the CTO date is before the date of issue. The 1991 World Cup issue makes the record, issued on 15th February, the CTO are dated 25th January.
For each stamp issue all CTO of it have the same cancellation date, but sometimes there are variations. The 1996 first definitive set gives a notable example. Issued on 30th January, the standard CTO date is 9th February, the variant shows 9th August:
The 9th August variant is rarely seen, in fact the date was meant for the second definitive set (issued on 30th July) CTO:
The COPREFIL contract ended in late 2001, since then Cambodia stops having CTO. From 1982 to 2001, only the surcharges, the 1988 Vietnamese printed Apsara 4v set, the 1993 Russian printed independence 3v set and the 2001 Vietnamese printed King's 80th birthday 13v set do not have CTO.