The Amiga Before the Amiga: The Amiga Development System
amigalove.com
amigalove.com
The lid was almost certainly injection moulded - which means you have two mould halves which form a complete mould. In this case, one half for the "inside" of the case (with the screw bosses and sprues) and one for the "outside".
The usual build process for these is to start out with the mould glossy, check the resulting parts for form and fit, make any adjustments needed.
Once the mechanical aspects are settled, the final texture (like the matt surface effect that a lot of PC cases have) is added as the last step. The reason for starting out with a glossy finish is because it's easier to make changes when you don't have to match a texture with every change.
The signatures were likely added to the inside mould by engraving or CNC cutting them at the same time the texture was added to the outside mould. I wouldn't expect it to be done by chemical etching, the process is too slow.
There would have been a tooling cost, but that's an NRE. Amortised over the production run, it probably added pennies. Depending on CBM's relationship with their toolmaker, it might have been priced as part of the texturing (which would have needed to be done anyway).
> The signatures were likely added to the inside mould by engraving or CNC cutting them at the same time the texture was added to the outside mould.
I'm also guessing that given the detail of each signature, this would have been digitally handled in RS-274 or a plotter language? The level of detail is so spot on that it's tempting to overlook the circa 1980s timeframe and what consumer manufacturing could do cost-effectively back in the day.
Another observation is that none of the signatures overlap with the internal support ribs...almost as if the image was transferred in sections. I wonder if the original design team signed a silhouette of the rib pattern, or if the signatures were post-processed to eliminate collisions.
We still run CNC machines from that era. At least one of our machines dates to 1979. While it would take a lot of tape there is nothing that I can see that makes those hard to do.
(Ours no longer use tape but a drip feed from a parallel port.)
Heck, if you're cheap, use two pots to make a two-piece digitiser arm and scan it that way (Mike Cook wrote an article in BBC Micro User back in the 80s about this). Measure the angles then do some geometry to figure out the Cartesian (X/Y) position of the arm. Create a point cloud, join the dots.
Once you have the outline, creating GCode would be a relatively simple task (for a computer).
Also I don't think the ribs are for support, though they will certainly do that. To me it looks like they're to allow the plastic to flow into the mould faster.
Hunt down the "Engineer Guy" video on injection moulding if you're interested in the details. It's a fascinating process. Simple concept, but the devil is very much in the details.
Interesting to see the reinforcing rib, missing in the release version, that's been manually nibbled away in the dev box.
More seriously, he admitted that the presence of the dog set a much informal tone in the office and made it easier to hire "unconventional" characters.
As for other machines, I don't know of other signatures, but there are often Easter eggs. Commodore machines had funny stuff on their PCBs: codenames Rock Lobster, Junebug, plus the Fred/Wilma LEDs, etc. Lots of integrated circuits from several companies had artwork in unused areas of the silicon die.