Ok so the whole thing stinks - there are gray areas. Definite no nos predating 1900 and definitely ‘modern’, that is this side of 1900 and then the gray area. The gray area can be a site the age of which cannot be determined or a site which was used up until say 1930 to discard rubbish but in truth was first used in 1840. A slick lawyer could argue successfully either way.
What about an 1870s dump/site that’s being eroded by the sea or a river? If you salvage items from there before they are gone forever then where do you stand. If you merely pick up something that has already fallen out of the bank and it’s about to get washed away then where do you stand? If you see goodies protruding from the bank and about to get washed out then presumably you are technically excavating by removing it.
My personal belief is fuck the text book Gestapo like trolls who given a bit of authority let it go to their heads as they are actually enforcing unfair rules and not only assisting to erode your rights but their own as well.
Take ship wrecks - you cant touch one older that 100 years or is it 1900 but the next storm could wipe it off the face of the Earth and in any case shifting sands, currents etc degrade it daily and yet if you remove even a long rusted bolt then you are in strife. A bit obscene really. At the same time if the vessel is truly historic then it should be properly excavated by marine archaeologists.
Personally l am a true blue Kiwi and no sniveling arsewipe is going to tell me that l cant keep that 1860s artifact that l have just found after all if l leave it there then when you walk by you will grab it. Nor am l going to rush off and grab the authorities because they will keep it. I know of quite a few small artifacts brought back privately from the restoration of a very historic site by a DoC employee so in my opinion regardless of its age you salvage it because that prevents it being lost for ever and it also protects it.As for leaving it and declaring it with the resulting mapping of the site and where ever shard of glass and piece of rust lies what is the point?