Nos radiators are very hard to find because:

1. They get beat up and worn out over time and need replacing.

2. the ones that sit on the shelf and dont get used go bad. Talk to someone who reworks old radiators....when I did, they told me that if the radiator isnt thermal cycled (get it hot, cool, get it hot, cool...driving it in other words) on a regular basis, the brass will become brittle and will crack when pressure is applied to it. I had one, it cracked first time I put pressure to it...took it to the radiator shop, fixed, took home, installed it, cracked again...thats when I had the discussion with the older guy who owns the shop and he told me about the brittleness issue...

So, if its truly NOS, its probably junk...

My $.02...