Ah, okies, alles klar!
If you weren't using the Reggiano DOP version of Parmesan before, then I'm not surprised you can tell the difference. We wouldn't use anything else.
Wee tip: a good way of judging the best Parmesan cheese is find the stuff that looks the most 'knobbly' and irregularly shaped. If it looks too smooth/refined, 'creamy white' in colour, and cut into a nice sharp triangle, the cheese has been more mass-produced, and is probably younger.
The rougher looking, darker, more yellowy coloured stuff is best, rather like that shown on this link: https://vinepair.com/articles/parmes...-grana-padano/
The differences between the various types of Parmesan are also explained there.
Marco.