What coils is this verified to work with?

AEM, Haltech, and Megasquirt IGN1A-style smart coils. eBay and newer Mercury coils may or may not fit properly.

What material and finish is it?

Billet 6061 aluminum, 3/8" thick, CNC machined (not waterjet), matte silver finish.

Autosports Engineering 1JZ Non VVTi Coil Bracket IGN1A Smart Coils
Features:

Billet 6061 Aluminum
CNC Machined NOT WATERJET
3/8" Thick
Grade 8 Bolts Included
Matte Silver Aluminum finish
Verified fitment with: AEM Haltech & Megasquirt Coils (eBay and newer mercury coils may/may not work)

https://youtu.be/YKMTX4HVoXQ