I do intend to retrobrite these at some point as they are a bit yellowed. Presently they are soaking in what I like to call "keyboard soup" to clean them since they are well loved but not well stored. A lot of typewriters will come with lids or covers which means that you can find them in good shape pretty often. No luck here though, maybe when I get the black cap version.
This confirms that the board was indeed made by brother for xerox and not the other way around. I had been curious about that so it is nice to settle that matter.
To get to the meat of the matter, and one of the main reasons why I wanted to get one in the first place, is the caps. Like most every proto-topre board the caps include several that are triple shot although on this board there are a lot less that usual. However, these are the only ones (to my knowledge) that don't use a proprietary mount that is at least similar to modern topre, but rather use a familiar mount found on quite a few switches. I don't have any switches at present that use this mount to test on, but from what I remember of the ITW mag valve switches I used to have these should be 2-way compatible. The stabilizers are still proto-topre mount for whatever reason and have really thick rod stabilizers so this board would not really make for good cap donors for a hypothetical hall effect custom or what have you. The layout is really nice though, so a way to use these would be excellent.
Weirdly enough the caps lock key is single shot probably. I am not entirely sure if the LED window was in injection shot or if it was inserted in after and melted in place. The legends on the cap are printed with a method that I cannot identify. It yellowed so that rules out sublimation, the legends are not raised which rules out pad printing. I supposed it could be infilled or printed very very well with some mundane printing method. I would love for some insight from someone with more knowledge on the various printing methods.
Sliders on these are a lot different than I was expecting. Unlike almost all the other proto-topre that I have seen they clip into the housing. And on these it makes them a right pain to get out. I was fairly certain I was going to bend the clip too far and break something but they come out just before that point thankfully. These clips are peculiar and contribute to the bizarre sound of these switches as the clips are quite bouncy and instead of a single clack on the up stroke you get a buzzing as the clips bounce against the top housing for a little bit before coming to rest. It is not a good sound in my opinion and makes the switches honestly kind of disappointing as the feel and sound is otherwise very similar to discrete dome and foil (which is to say they are nice domes; smooth and the tactile is good as well) since the clips on the slider result in a solid bottom out instead of a mushy bottom out that you get on a lot of other dome boards that bottom out on the dome mat directly. The upstroke buzz sound just ruins it. I'll try to get a sound clip uploaded so you can hear what I mean. They sound a bit like frogs.
Despite what I was hoping they are not discrete switches but rather share a communal plastic top housing. There is a layer of metal foil on top of the plastic top housing that serves to shield the keyboard and it makes it look like the switches are in a switchplate. This is not the case unfortunately. It has two flat metal rods that run the length of the board, presumably to prevent flexing. One of these rods can be slid to the side to allow access to the space bar stab wire so that the assembly does not need to be opened to remove the space bar, which is a really nice touch that not all brother boards share.
For the internals is, surprisingly, a capacitive membrane. You could argue that this is more properly a flexible PCB and not a true membrane but I think that definition is unnecessarily restrictive when functionally a membrane as a category of keyboard component is just a conductor stuck to a very flexible piece of material that gets used as a replacement for both the PCB and for discrete contacts (or equivalent) alike. What that conductor, flexible material, and sensing method are will change from board to board and the perception that membranes aren't mechanical will be present even if this is classified as a PCB since anyone with misconceptions like that about membranes won't know the difference anyway.
Anyway, pedarntry aside, the double sided membrane is interesting visually even if functionally it is just a more fragile version of the PCB alternative. They had the guts to solder an LED to it which I am impressed with even if it does present a potential concern when assembling and disassembling the thing. There does not appear to be any layer between the membrane and the 2mm thick back plate. I'm not knowledgeable enough in how cap sensing works to know if there should be or what, but something is attached to the back plate when it is assembled so it is probably involved with shielding or something of that sort. The metal foil on top of the plastic housing is also connected to the membrane in the same place as the back plate.
Not the marquardt I'm after, but it is a nice switch nonetheless. Keyboards aren't the only place where the switch choice matters.