I was initially confused about why just the middles appeared to have been filed away and like you, thought it was possibly just some cleaning up.
My initial thinking was that it was possibly one of the caps with the "vampire fangs" at each end of the twin slot but only one side had been filed. I had forgotten about the long slot variant with the lowered middle.
You pictured it ... on the right
This is the bit I believe has been filed out so that the cap fits the other twin slot baseplates. So absolutely the right kit: top cap, baseplate and handle. Just modified.
... also used in the "long slot" Tech:
The lowered middle section is so that the handle can nip up fully. Curiously, not an issue on the RFB, leading me to believe that any such top cap was leftover from the probably aborted run of "long slot" Techs, given how few and far between they are.
We've seen it time and again in the automotive market; special models, special editions made up of surplus stock and leftover bits.
They made a long slot NEW Service Set version as well, so it is entirely likely that either the Tech or NEW version could potentially be where the top cap may have come from.
Unfortunately, I don't have any photos of the underside of the top cap, however, I think they were identical to the one used in the RFB.
More than a 'Fount of Knowledge'...you guys are more like a Tsunami of Knowledge.
Thanks so much. Yes, I'd sort of figured that some clown had filed down a long slot cap.
Now I just need to decide if I try to find a good cap...or just swap/sell what I have.
I used the Tech today just because it was out and assembled...but really prefer my Timeless/Karve/Blackbird etc.
I could also (I guess) just use the cap from my lovely NEW SC...which quite seriously will probably hit the BST soon as I haven't used it for a couple of years now.
Much appreciate all the input.
Just found a Gillette NEW LC locally, and not too dear.
If I'm reading all this correctly then no harm for me to use that LC cap?
Thank you guys for all that info...really is much appreciated.