I kept clicking "multi" quote to see whether this got answered. I don't think it completely did, but that's a German size. It will be around a 52L. There are regular sizes (EU 48, 50, 52, etc.), but long is not often marked "long," but rather 98, 102, 106, etc. Short, on the other hand, is ca. half of a regular: 24, 25, 26, etc.
It's an awful system, but I haven't seen it much outside of the German-speaking countries. That said, I see it on non-German brands that are intended for sale in the German-speaking world, i.e. PRL. I posted SuitSupply's size chart a couple of years ago, but here it is as a guide: