This month's MRH includes an announcement: "Accurail's list of new HO scale car kits this month is a 40’ AAR steel boxcar built in 1959 and decorated for Frisco – St. Louis & San Francisco." It is currently showing as available on the Accurail website.
Here is a picture of the car from the Accurail website. It's stock # is 3544. The MSRP is $16.98 and an optional decal set (stk.# 3544D) for renumbering is available for $4.00. .