These fronts can also be found with the Jos. Stiner & Co. back
http://www.b-lauctions.com/site/bid/...sp?itemid=5634
The Risido back that Rhett mentioned above is definitely the high dollar back. I've seen some others with the Merchant Tailoring back, but I don't have any pricing info. For yours, I'd guess $150-$200 each considering their condition.
Best Regards,
Craig