Hi John, If it was me doing the test, I usually like to see at least one previous certificate (preferably the first one if a commercial build) and also drawing / construction details.
Once I've ascertained the heritage of the boiler I would treat the test as an unknown and require the boiler to be removed from the frames and all cladding / insulation / fittings removed.
The test can then be carried out as if 'new' with a full inspection and hydraulic test, this will enable the first set of insurance details (boiler record) to be set up with the necessary logs.
Upon reassembly to the frames the remainder of the test can be carried out (Steam test, safety valve blow off, gauge test and marking, and sight glass blow down if applicable).
Following satisfactory completion of the above a new certificate will be raised,