The professional series are laser welded down the full length of the grating surface, and Microplane emphasise this. Looking at these ones, it doesn't seem to be the case (although it's hard to tell from the photos), and it doesn't say anything about the welding in any marketing materials. So my guess is that they've reverted to a cheaper and faster method of production. If so, it would be a pity to have the "made in the USA" version be poorer quality than the "made in China" version.