At my first visit to Austin Garage near Burton on Trent it was pointed out that the rear springs on my mk1 ZT 260 had been replaced by mk2 springs.
Nick the proprietor explained that the early springs were prone to breaking and when they do they should be replaced with the improved mk2 springs …… which must have been the case.
I recently read an article that the way to tell the difference between the mk1 and mk2 springs is that the mk1 springs are close coiled at the bottom whilst the mk2 springs are close coiled at the top.
MG ZT info mods and maintenance 