There's a further clue.
When I pulled out the damaged keyboard assembly, I'd tried all the intact buttons. All work fine except this one:
Whut? Is that... hot melt glue? Why yes, it is. Whoever stuck it down got glue under the switch as well, which of course stuck down the button plunger. I thought that was why the leaf spring was held bent. But no... after gently cutting away the hot melt glue, avoiding damaging traces, I was astonished to find that isn't an original leaf spring. It's a piece of tinplate, apparently cut from a tin can. It has no spring at all, and is permanently that shape.
I can't even... it's like someone with the capabilities of a 6 year old was messing with this machine.
Speaking of childlike, take another look at 02_front_3.jpg above. Top right corner of the pic. See it?
After I told him how to remove the top cover to take a photo inside, he put it back with the right side cover popped out. I asked him to redo that with the side covers properly in place before packing for shipping, and he did. Point is, he didn't notice this himself.
Here's another interesting 'feature' in a pic from the 2nd seller (and also visible in the 1st seller's pics.)
What do you see? Apart from the valliant stickers bravely protecting the machine's last two critical screws, the special screws from the HP-IB socket are gone. The black ones with threaded receptacles in the head, for the cable plug to secure to. But... they have been used to secure the fan cover. (Then because they stick out, one of them was sheared off in shipping the machine to me.)
The 'screw remover' decided to keep the fan cover on (for the photos?) using the only screws from the entire machine that weren't shiny stainless. The nasty black, odd shaped ones. Went to the trouble to pick them out of (presumably) his tray of extracted screws.
But this person, who can't get the top and bottom covers off a HP machine, _surely_ isn't collecting screws for use in repairing other HP machines. He knows nothing about such machines. He's just wanting 'shiny screws.' Maybe even just for scrap stainless steel?
Summary - I got a spares machine semi-intact, all due to two tiny thin stickers thwarting a child-like person.
And I have a pretty large stock of suitable stainless screws, so was able to replace all the missing screws with correct types.
Wrapping up
This is the 'spares' unit, with good front frame removed, and also the side struts. I had to disassemble it a bit more, to get at brackets for the mains switch actuator shaft, that were loose inside due to 'the someone' removing the screws that held them to the side plate (at top here.) Also to get the display unit out to test it.
The machine partially visible to the left, is a HP 3562A Dynamic Signal Analyzer. It had a bent side strut (see
https://www.eevblog.com/forum/repair/hewlett-packard-by-salvador-dali/ ) and I'm waiting on a replacement strut in the post. Ah ha, but this 4145B has exactly the same struts! I'd like to complete and close up the 3562A, so used one of these struts in it. The 4145B can have the one coming in the post.
The damaged front frame, I'll make an attempt at repair and put it on the spares machine. If the repair looks crappy, no matter.
The vector display works! This is its self test pattern.
Screws 4mm x 8
In a discussion about the 3562A, someone asked where to buy the special countersunk screws used in the HP diecast frame corners. Here's some suitable replacements, sourced from Aliexpress and cheap. They are M4, 8mm long, standard countersunk heads. They are slightly longer than the HP screws, and project about 1.5 mm inside the frame. But in that area there's rarely if ever anything hard against the inside of the frame. Just check it first, usually will be OK.
PS. If you are ever replacing one of these 4145B front diecast frames, watch out. It looks completely symmetrical, ie rotating 180 degrees should make no difference. But it is NOT. The left and right sides have very slightly different structural screw hole positions. It's quite confusing when you put it on the wrong way at first, and the screws don't quite line up.