The key (I hope!) is that the document is described by FMP as "WO 23 - Royal Hospital Chelsea: Admission Books, Registers, And Papers 1702-1876" - in other words, we are looking at something written from a pensions viewpoint. At the top of that column it says "District 1865" - which it isn't, of course, since he's not even joined up in 1865, they've simply written in the first empty column. I think it was when I saw "Date of Admission" next to it that I twigged what I was possibly looking at - it's the
Pensions District, not a Royal Engineers thing.
I have no idea whether there is an up-to-date version of
https://webarchive.nationalarchives.gov ... itle=WO_22 but that URL lists the Pensions Districts and it confirmed one of my wild guesses at that squiggle, which is "2nd Portsmouth" - or, "2 Portsm'h" as it's abbreviated.
If you scroll down the linked page, you'll find (and I knew none of this before) a table of the Districts and the Pay Offices within them. 2nd Portsmouth District has several Pay Offices, including one at Farnham, which is not far from Aldershot, which was CWS' Intended Place of Residence, according to the last page of his Discharge papers. So that's where he'd have gone to pick up his pension for however long he got it.
(And I have no idea why Aldershot, of all places, didn't have its own pension pay office!)
Retrospective thanks to the late-lamented Victorian Wars Forum for providing the answer that - fortunately - I copied years ago.