Veteran air carrier Captain describes deficiencies associated with QRH terminology and identification of the correct QRH to be used with a mix of different aircraft model variations resulting from merged carriers.

Narrative

[My airline] has always been a leader in the industry when it comes to safety.... With this in mind; the last round of what some consider training for the newly released...QRH is at best; marginal. Most of us have been with [the company] in excess of 20 years. We have a long history with the terms and acronyms regarding aircraft systems. Unfortunately; the QRH uses many new terms; system names and checklist titles making it difficult enough to find the correct checklist; even when not dealing with an emergency situation. Many of the checklists titles contain suffix letters which are supposed to help identify which of many similar checklists apply to the aircraft which we are operating that day. Unfortunately; the suffix letters don't match the newly installed placard on the instrument panel.... Currently the letters on our trip ID; the panel placard; and the QRH probably do not match. A bulletin was issued to help us determine which panel placard applies to which QRH checklist. Why is a 'decoder ring' needed to determine which checklist applies to our aircraft in an emergency situation. When the fleets are merged; there will be 12 derivations.... Which checklist do we use today? There is no good reason that the QRH shouldn't be aircraft specific and include only the checklists that apply to the aircraft in which it is installed. At a minimum; the panel placards should match the QRH.