I did some casual digging into "salt beef"/"corned beef" usage. The history is a bit murky, unfortunately. "Salt beef" is the popular term in London, where they even have delis with "salt beef" in the name. (Also, English salt beef is not interchangeable with American corned beef.) However, it isn’t clear to me if this was always the case (salt beef was not a hot topic amongst my British penpals).

From Wikipedia:

"Corned beef is known specifically as ‘salt beef’ in Newfoundland and Labrador, and is sold in buckets with brine to preserve the beef. It is a staple product culturally in Newfoundland and Labrador, providing a source of meat throughout their long winters."

So there’s the Canadian connection, again.

And a poster on this thread (and elsewhere) mentioned Navy rations. Which is another way Z could have been exposed to foreign culture — if he was in the military and stationed in another country.

However, on Newspapers.com, there are definitely a lot of hits in American newspapers for salt beef.

"Happy Christmas" — again, this is more popular in the UK, but one quick look at Ebay and you’ll see "happy Christmas" on a lot of American things.

Like most angles on this case…YMMV. You can make a case for it, you can make a case against it.

So if corned beef is made with salt is salt beef made with corn? I think that’s the real question. I discussed the Britishisms in the Zodiac letters and I didn’t even use any reference to Salt beef or corned beef.

The haughty, dry tone ("I am rather unhappy that you people will not wear some nice [Zodiac] buttons…") does put one in the mind of Masterpiece Theater presentations, yes. I think we were inferring as much a couple pages ago.

And "Best get off their fat asses" — an American would typically say "better"…

P.S. I’ve never seen this article by Hewitt. Interesting that he made a case for "this is (____) speaking" being a Britishism, since his suspect is Ted K.

Salt beef is not made with corn. Salt cured beef is a product famous in Newfoundland and Labrador, in my neck of the woods, and also in the rest of the maritimes of Canada. It is small pieces of raw beef or pork ribs, stored in a bucket of heavy brining ” pickling salt” and place in a fridge or cold storage.

Oh, I’m 99% sure he was joking about that. Although, 2020 isn’t over yet.

Anyway, I pulled up Mark Hewitt’s PROFILED on Kindle: "Upper-class British parents teach their children to use similar words for answering the telephone. In one James Bond movie, the titular character picked up a receiver and greeted, “This is double-O-7 speaking.” However, he also points out that airplane pilots say something similar ("this is your captain speaking").

I can think of another example that was mentioned here years ago:
"This is Alfred Hitchcock speaking"
https://youtu.be/hg9MDm3JjYs