Jack
20 sump'n years ago I had a ton of Sonor stuff I was buying and selling. I took a lug and tension rod to a local powder coating company. This company was very experienced and did great work. We also had a before and after conversation about the results of powder coating with the intent to match decades old powder coated parts. If you are considering getting some done, please keep in mind the following...
Largely, blasting process (whatever medium they decide to use) only preps the surface for adhesion to the new finish. Pitted parts have to be sanded to remove the craters left by the pitting. Luckily, the HiTech parts are a flat finish so you can get away with things slightly better than if high gloss. Quick example of that is if you have even seen where a well used freight car has been repainted, you can see all sorts of dents from loading and unloading.
Another thing to consider is threads. Surprisingly, even though the lug (inserts) and the rods were both powder coated, they still married smoothly despite the extra bulk. But, again, the powder coating was expertly applied in this case.
How does it match the original? Well...
Like paint, the challenge is that there is no telling who manufactured the original power. But, even if you DID know, you could never expect a match since years old powder will be oxidized. So, you aren't trying to match it as it was then, you are trying to match it as it is now.
Did they nail it? Nope. Not possible. (Not practical, at least)
The parts had more of a sheen than the uber flat parts I had that had been done at the factory. It was likely a combination of variations in the powder product itself coupled with time, as already mentioned. Was it good enough?
Was it good enough? That's certainly subjective. If you were refinishing a few chipped up pieces, I would think it was acceptable. If you were refinishing a huge batch of parts and there wouldn't be a mix of old and new, certainly acceptable. If you were assembling a piece that would pretty literally going to be a museum piece (to wit: was going to be viewed and close up and potentially scrutinized) and were only doing select pieces, then it would be noticeable to someone who was aware enough to know to pay attention.
I don't have any photos any longer of the pieces I had done. But, it was good work and I was happy with the finished product with investing hundreds and hundreds of dollars trying different powder brands, hues and gloss blends.
Hope this helps. 