Update:
Been thinking in advance what to do to label the knobs and switches... laser engraving or mill engraving. It affects the pricing. Or maybe I should just leave it unlabeled.... hmmm... still thinking.
Preamp looks great!
Guess it wouldn't make or break for me if unlabeled, although I'd pay more and would prefer to have mine labeled. In the grand scheme of things, just thinking out loud that it might not be as well accepted outside the TS.com community if it's unlabeled...as if it weren't a professional product or something. Besides, why go as far as you have, with the ULTRA superior professional approach that you've taken getting the preamp to 98%, only to leave the product looking 'home-made'.
Even though in this community, we know what's inside the box is what counts, it's what's outside the box and how it looks that may convince many (if not most) potential non-TS.com buyers as to the professionalism that went into design and construction. A home-made looking end product implies a home-made approach to design and construction and devalues your product, IMO.
My $0.02 anyway.
EDIT TO ADD: If it was me, I'd personally even go so far as to make sure all exposed aluminum in the cut holes are also somehow colored or blackened so that there is no exposed silver aluminum showing from the exterior, but that's me because I do think presentation is important to the end product.
(An analogy is that I'm an engineer and my end work product is oftentimes a technical report. I can do a fantastic job and spend years on a project doing nothing but Grade A technical work and present a final report that is 100% technically correct and technically outstanding, but if the report has typos, incorrect page numbers, wrong references to figures, etc., then it shows a lack of attention to detail and generally leaves a negative impression, especially on people that read the report but don't know me or the work I've done.)