[Arran]

 If it's like the last Philco IF can I took apart you will have to remove the can from the chassis first to get the cover back on once it's removed. There is a clip that is near the base of the IF can, and this clip fits through a pair of matching slots on opposite sides, this clip must be removed to get the cover off and be re-inserted to hold the coil form in place, both are much easier to do with the can removed from the chassis.
Regards
Arran