When all else fails:-

R.T.*.M.
I think I mentioned my trip to Cranston's, whence I never leave with as little as I entered for.

Since Alice died I have, actually, made these a few times; never, of course, quite up to Alice's standard - but edible. ;¬)
Apparently they are neither "Soused" not "Pickled", though Al NEVER said they were a "Tray-bake" either.

Ye internet quoth thusly:-
"Recipes > Seafood > Herring > Herrings baked in Vinegar."
 
I spotted these at the fish stall when I bought a couple of unintended kippers. 
"I wonder if they're up to Al's standard, I'll soon find out; but they look a bit undercooked."
Tried to lift by a dorsal fin, expecting it to come off - NO JOY.
Lifted one out - eventually - tried on a short unrolled section, to remove skin - NO JOY.
Bug writ and BUDGIE-grit!! They're ruddywell RAW, only look lightly cooked.
Now cooked, but since I've other plans for tonight, concerning a "Hen-titty" - stuffed kinda Kiev-like.
I used to insert a sharp, pointy, knife and sort of quarry a cavity, which we'd then fill via Alice's piping bag. That's tonight's "Tea". (I've never been posh enough for things like "lunch" and "dinner".)
What did surprise me was that when I lifted one out there appeared to be ZERO liquid therein. As I lifted them out I had to be careful not to spill the juices, now brimming the container.
:¬ O

Addendum:-
They're a damsight bigger than the ones we could usually buy.