Credit Suisse issued its latest non-agency jumbo mortgage-backed security last week and, in a change of pace, included a significant portion of 15-year fixed-rate mortgages in the deal. The $597 million CSMC Trust 2013-6 included mortgages that have seasoned for an average of three months with a weighted-average coupon of 3.56 percent, according to a rating report from DBRS. The seasoning on the mortgages wasn’t out of the ordinary compared with other recent issuance by Credit Suisse, but the average ...