Just heard from Tim Hollis who read this item and has this to offer…
Your friend Andrew Leal is correct that our ol' buddy Dal McKennon was Uncle Scrooge in the Donald Duck and His Friends album (I believe it was released in 1960). Greg and I have commented on the fact that Dal chose to give Scrooge a Scottish accent with no apparent precedent (obviously Scrooge did not speak in dialect in the comics). Then, when Bill Thompson did Scrooge in the 1967 educational cartoon, he continued using the Scottish accent; we have no proof that anyone at Disney played the record for him so he could see how Scrooge's one and only audio appearance sounded, but he picked up that accent somehow. Of course, Alan Young says that his Scottish accent was a genuine remnant of his own upbringing, and he had probably heard the Thompson voice if not the McKennon one. The fact is, though, that in that one LP, Dal McKennon inadvertently established how Scrooge would sound from that point onward.
(As an aside, that 1960 LP also featured the sped-up voices of Dick Beals and Robie Lester as Chip 'n' Dale respectively, but that's another story from Mouse Tracks.)
Okay, this settles it for me. And just to remind everyone: Mouse Tracks by Tim and his partner Greg Ehrbar, is the definitive (an adjective I use sparingly) history of Disney records. You can order a copy here.