Whoever you spoke to at Lofrans is wrong, very wrong. Did you download the Anchor Chain, Galvanized dimensions and calibration.pdf.
Please read it and you will see that 10mm chain is made from 10mm (3/8") stock which is manufactured in what most people refer to as two different "pitches" (pitch is referring to the dimension of the link, not the stock). The DIN766 has links that are 2 mm different than the ISO4565 standard. DIN766 is 28mm long and ISO4565 is 30mm long. These chains will NOT work properly in the same Gypsy...different Gypsies are required for each.
I have found that most people do not get their heads around the difference between ISO4565 and DIN766, mostly because there is not a common and accepted way to explain the difference...let me try...
ISO4565 and DIN766 each are made with 10mm stock. The difference is that the size of the links are different. Now to really confuse you, if you compare any other size stock, like 8mm, or 12mm, the links are identical sizes with ISO4565 and DIN766.
Your 10mm chain needs a different Gypsy for ISO than DIN...but only if 10mm (3/8").
I really hope this solves your issue and helps you get what you need.