Dec 30, 2010 - 3:14 PM
You don't need to posses your Swiss Half Fare Card in order to arrange for seat reservations. The seats can be booked separately through the page I linked to in my previous message. The (discounted) tickets Chur - Zermatt can be purchased in Switzerland, or online. As long as you have all 3 documents (Half Fare Card, tickets, seat reservations) when you board the train, you'll be fine.
Does this answer your question?