Here are the codes on the PCB for anyone curious. PCB of the Penman for comparison. Penman's PCB was not made by ALPS and I am almost certain the switches weren't made by ALPS either even though I think the keycaps were. You can also see that the plate has large gaskets that are held between mounting points on the case. When the bottom case and top care are screwed together both case parts press on the gaskets from above and below while a peg in the bottom case goes through the middle of each gasket which keeps them in place. It's a decent mounting system IMO that would likely be nice to try with a modern board but with the bend steel plate there's not a lot of flex in the thing and since it's a typewriter with clicky switches (that aren't DIN compliant at that) the sound and feel aren't effected the way a modern low profile board would be. I suspect it would be nice if done correctly, but it's hard to tell based on this particular execution. I think this is similar to burger mount or possibly gasket mount in some ways. Interesting at any rate.
Anyway, on to the caps and why I suspect the keycaps are ALPS made.
As you can see from these pictures, the mount on the cap is incredibly close to that of known ALPS caps for short SKCC which have some extra geometry at the interior angles of their cruciforms that make them incompatible with many other caps. The fact that these caps are compatible with that particular mount is highly peculiar especially when SKFF does not have extra geometry at the interior angles of their cruciforms like SKCC. If silver reed was making their own caps and merely buying switches that fit their existing mount then it would be a little strange for them to be compatible with SKCC which as far as I am aware is not as old as SKCC although I don't know if there is hard evidence of this honestly.
In my opinion that line of reasoning makes ALPS a sensible manufacturer for the caps on its own, but doesn't rule out the possibility that they are just a very good copy or the compatibility with SKCC is accidental. However when you look at the space bar stabilization for the Penman you can see that is very clearly isn't the sort of stabilization that ALPS used:
But the molding of the Penman's spacebar is very similar to that of an SKCC keyboard's space bar. There is a "notch" of sorts on the central mount which on SKCC is for stab wire clearance and the 2 T-shaped protrusions to either side of the central mount slide against the ALPS style spacebar stab mounts to provide additional stability to the spacebar. On an SKCC or SKFF board with alps stabs they do just that, but on the Penman, which used completely different switches and different stabilizer hardware for the spacebar those elements don't make any sense. These are the elements that make me thing most of all that these keycaps are made by ALPS themselves as they're way to specific to ALPS for someone else to just clone willy-nilly. I'd expect at least some of these elements to be missing or significantly different if Silver Reed was aiming for compatibility of their own caps.
And on a final note for the keycaps, a lot of them are molded strangely, you can see in this image from another post that the supports that go between the mount and the sides of the cap are sometimes incomplete for whatever reason.
On some keys the support is missing a significant amount and essentially not connected at all to the rest of the cap. SKFF stems have 2 nubs on them that sort of "snap" into indentations within the cruciform of the cap. for single unit switches like the above pictured cap the slider inserts into the cap with the nubs on the north and south of the cruciform. This nub, combined with incomplete support on the cruciform means that the mount on the cap is weakened and may break off partially when caps are removed. on caps where the nubs are east/west this does not seem to be an issue as the nubs don't exert any force on the weaker part of the mount.
Here's what a broken stem looks like. In total I broke 5 caps while removing them, all single unit caps and all from the home row. They don't seem to have any trouble staying on the switches with these missing pieces and I don't think there is any surefire way to prevent them from breaking so while it's a pain it shouldn't ruin the caps. If you can manage to keep all of the stem pieces you should be able to glue them back in place, and I would recommend using some sort of epoxy or plastic glue or something to sure up the supports on these caps to prevent any future issues. Hell, simply filling all the empty space with epoxy/resin since they're non-DIN compliant and the hollow space in the cap isn't used for anything would probably be the best bet and it what I'll probably do when I get around to it.
As a typewriter it's nice enough, the ribbon cables that go from the keyboard module and to the brain in the back of the machine have an exposed connector in the front of the machine that would probably make testing a dead keyboard easier or allow for peripheral attachment of some sort although I haven't looked into it too much. Other than that it doesn't really have any cool features beyond what any other top of the line daisy wheel typewriter of the time would have so unless you don't have an electric typewriter this one doesn't really entice any more than any other daisy wheel typewriter. SKFF isn't as nice as the dome switches the Penman uses (this is perhaps a hot take but I stand by it) so it isn't even the nicest typing experience Silver Reed machines offer. They aren't bad switches, but the ones in the Penman are very nice domes, more tactile and lighter weighted. Maybe if SKFF was a lighter switch they would be closer but stock the Penman's domes are nicer to me. I still stand by my statement that the IBM Model 65/85/95 is the best electronic typewriter you can get and the EX 55 doesn't offer any features that the IBM is missing to make me switch to it ever. Cool switches, cool caps, machine is average.