On the web sites of many mastering facilities, you'll find a page that lists the gear they use for mastering.  Most list their gear
for the purpose of giving their potential clients confidence in their mastering abilities.  There is certainly nothing wrong with that. However, when searching the web for a mastering facility, thought is seldom given to the ability of the engineer.  The engineer's ear and decision making ability, along with full range monitors and a well tuned room, are without a doubt the most important pieces of gear used in the mastering process.  Yet these are generally ignored by those searching the web for a mastering facility.  Their emphasis is always on the facilities gear.  Gear is important, but it should be a secondary consideration.

Like most mastering facilities, we use gear not usually found in recording studios.  For example: the most popular DAW is Pro Tools.  It's a good tool for tracking and mixing, but many are surprised to learn that it's not generally used in the mastering profession.  We have been asked many times by potential clients if we use Pro Tools.  When we answer no, the conversation is usually cut short and the potential client moves on.  That's unfortunate because they have fallen victim to marketing techniques created by equipment manufacturers.  Pro Tools is a fine tracking and mixing program.  However, it is not a program designed for mastering.  Mastering facilities that do have Pro Tools in their arsenal, use it primarily for playback or processing.  They do not use it as their master recorder/editor because it's limited in the tasks that it can perform.  Example: No CD authoring.

What gear do we use and why isn't it listed?  Except for some basic ITB plugins, our gear is custom built.  Some of our gear is vintage and is maintained on a regular basis to insure the best performance.  Because our gear is custom built, there are no identifying brand names or model numbers.  Therefore, no way to list it.

We use PCs that are designed and custom built by us.  They are tuned specifically for audio and are powerful "dedicated audio" computers.  As far as software goes, we use Sony's CD Architect for CD assembly, and we occasionally use plugins from PSP, Waves, Voxengo, FabFilter, Sony, and others.  Except for digital limiters, plugins are not our bread and butter mastering tools.

Whether a mastering engineer uses custom gear, or well known manufactured products, mastering can only be successful if the gear being used is guided by experience and engineering ability.  It's the engineer (not the gear) that listens objectively and makes the right decisions.  The talent to make the right decisions cannot be found in hardware, software, or plugin presets.