Look at the following - avail on EASA website:
COMMISSION REGULATION (EC) No 2042/2003
of 20 November 2003
on the continuing airworthiness of aircraft and aeronautical products, parts and appliances, and on
the approval of organisations and personnel involved in these tasks
In particular article 7 "Entry Into Force" October 2005 is significant.
Also see
Pemco Aviation Group Inc
Forgot this, STC is SA2969SO for the cargo door.