Leviton Hospital grade 20 amp outlets?

Are there two types of this outlet? One nickel plated and another brass plated? Which one is better suited for audio use? I have used the 8300 nickel plated version. What is the part number for the brass plated version?
If you are speaking of the contacts of the Leviton 8300 Hosp grade receptacle, the standard 8300 Hosp grade recept is unplated brass.

If you are speaking of the supporting strap, yoke, I am not aware of any Leviton Hosp grade recept that has a strap anything other than steel.

Hubbell on the other hand makes two 8300 duplex recepts.

The HBL8300, nickel plated brass contacts and nickel plated brass supporting strap.

The HBL8300H non plated brass contacts and non plated brass supporting strap. This one is said to sound better than the nickel plated recept. The HBL8300H is the cyroed recept that Albert Porter sells, "Porter Ports."

Another Hubbell recept to check out is the 5362.

If your branch circuits are installed in conduit try the Hubbell 5362IG, isolated grd recept.
Check out Oyaide gold outlets as they are very smooth and better than the mentioned ones above.
The Leviton Industrial Receptacles PDF gives the catalog number as L8200 for 15amp and L8300 for 20amp Hospital Grade non-plated brass contacts. The mounting strap is also non-plated brass.