Can I be sure of correct replacement part before making purchase?

I'm needing what the handyman called a multi-point mortise lock latch replacement. They look similar to the ones on your website. Can I be sure of a correct replacement part before making a special order purchase?
I think the wise place to start would be having your old sample to be sure. However, if you can send us good information, photos and complete our mutlipoint lock hardware Questionnaire - I'm sure we can solve your problem.  

MASTER MULTIPOINT LOCK SYSTEM PARTS ID GUIDE [PDF] - http://tinyurl.com/p4geg29