The X suffix applied to both the type and c/n is an internal Transport Canada code and refers to a special CofA for aircraft within the Owner-Maintenance Category. There is a brief description on the COPA website (quoted below).
“The Owner-Maintenance Category was developed to allow certain certified fixed-wing aircraft to be maintained, modified and upgraded under similar regulations as amateur built aircraft. In the mid-1990s, recreational aircraft owners expressed their concern for the spiraling cost and lack of availability of certified parts and expertise for older, unsupported aircraft.
“This concern was turned into a proposal from several aviation associations, including COPA. It called for a new category for these aircraft that would allow owner-maintenance, part substitution and aircraft modification. An Owner-Maintenance Category became part of Transport Canada’s new Recreational Aviation Policy in June 1996. That policy was accepted by the aviation community and approved by the Minister of Transport.”
If any owner wishes to put their aircraft back into CofA state, it would probably be quite expensive.