Expanding on Stallie's answer, one of the problems occasionally seen (and I presume from Leaddie's comments that this applied to the 767 - I neither flew, nor had any engineering involvement, with that very lovely passenger's machine .. enjoyed many pleasant pax legs around the network back in the days when the cabin crew had time to look after details such as wine, meals and nibbles) was consequent to a datal out of step regulatory change.
Typically, an aircraft missed a rule change in the country of manufacture (eg with FAR 25 A/L 42 in this case) due to the date of design standards freezing (ie where the OEM and FAA agree that the aircraft design will be subject to whatever version of the rules) occurring prior to the rule change effectivity.
Unfortunately, the first example of the aircraft might then have been imported to Australia after the date of an equivalent rule change here (in this case, ANO/CAO 101.6 at A/L 62). The importer then was subject to the local rule and had to run around a bit (read "spend money") to sort things out.
It always bemused me that local rule changes didn't have a suitable savings clause to provide a "get-out-of-jail-free-card" to cover this silly sort of situation where the local importer would be pushed to additional certification cost solely due to the datal mismatch.
My view was bolstered by the occasional inconsistency .. eg with ANO/CAO 101.22, for lighties, for years we used A/L 2 which worked fine .. in the main, for piston aircraft. Then it was raised to A/L 3 to cover turbines .. no good, it caused some problems for Nomad, as I recall .. so up to A/L 4 to address that concern.
Silly thing was that A/L 4 created some problems for the piston fraternity .. so the Regulator ended up accepting subsequent work to A/L 2 for pistons.
For the life of me, I couldn't see any philosophical difference between the .22 and .6 situations had a similar philosophical concession applied for datal mismatch problems.
However, I was just an engineering Industry grunt so not for me to get too worked up about things over which I had no control ...