I have an early 90's Wilson TPA XVIII that I want to restore. But before I touch it I wanted to know what the head is made from. If someone could let me know and any tips on restoration would be appreciated. Would be better to get it sent to get it done by Black Oxide as it is a one of my favourite putters.

You could also think of powder coating it if it would work with that metal. There was a place called custom club coatings but I am not sure if they are still around.

Mate, I bought a couple from Lamont that was refinished by i think Byron. Unfortunately, i'm overseas at the moment so unable to post pics. Mebbe when he reads this thread he can help. If not, i'll do so next week.

Try sticking a magnet to it. If it sticks, it is likely carbon steel and would make a good refinishing candidate. If it doesn't stick--it certainly is stainless and your options are greatly limited.

Boss,
I think it is a crapshoot as far as material on these putters. You might get some that are high carbon content steel, and some that are mostly stainless steel. I am not sure exactly what mine were made of, but Byron did an awesome job on them. I had him do a XVIII and an X for me, a couple of years ago. They turned out gorgeous.
I agree with the poster who recommended the magnet test. If it is carbon steel, yes, you could have it black oxide treated and be happy. If it is stainless, I have not heard good things regarding the Black Oxide treatment, over time.
If you are willing to give the putter up for a time, give Byron a call and see what he can do for you. I wouldn't hesitate for a moment with turning him loose on another of my putters. He was awesome to deal with and did a tremendous job.
Best of luck and let me know if you have any more questions,
LaMont in AZ
PS, I included a pic of the Crenshaw that he did for me, as well. I had it copper plated and it turned out absolutely stunning. That is also an option with your Wilson. The tuff part is deciding.