This sounds Scottish-levels-wet to me. Sopping. Drenched. (To be clear -- nothing wrong with this, but it does mean you have to change your shirt more often.)
You can count the "beats per second" on long notes like the one at the 10 second mark. It's more than 5 bps, so a greater than 20 cent spread. To try to get more precise, there are two long notes at this point: a long D5, followed by a long Bb4, so just a half step higher than the A at ~440 where you'd normally take a reference measurement. It sounds like it's around 7 or 8 bps (just patting my leg while saying 'One Mississippi,' but you could use a more scientific method with some sound software). So I'd guess the spread to be around 30-35 cents!
If this accordion had been wet it would probably have sounded worse!
But the tuning is indeed rather wet, but actually quite pleasant to listen to. Could be MMM with something like -20 0 +20. But that's just a guess.
I just took a listen to this piece and it is definitely an accordion. It's not nearly as wide as Jimmy Shand. As a matter of fact I'd hazard a guess it's Jack Emblow who played on a load of TV stuff at that time. We normally associate Jack with a Jazzy Bassoon Reed sound but I know he also had a pretty decent Musette. I'm fairly sure he did the Bergerac theme and I saw him in Secret Army and Some Mothers do
ave em using the Musette sound. Also check out Musette for a Magpie on YouTube with Martin Taylor. You can really hear it there. Flambards was a great series.
Jack Emblow also quite regularly played accompaniment on Sing Something Simple.... A sunday afternoon radio singalpng show.... Hated it when i wad a kid.... But did go see Jack Emblows farewell concert in some broken village hall, nice guy, great player but alas the box was too heavy for his withered frame so he sold it to my friend Stan and settled down to quietly reminise....
Played with Tony 'the Guvnor' Compton who's superb playing was totally trashed by the awful midi tones he'd chosen to use.....