I would have to guess early to mid-50's based on the styling (tho I'm no expert here).
I would LOVE to have one, if they ever existed or if any still remain!
272 RPM - leisurely? Not compaired to the '57-'60 Kenmore/Whirlpool combo @ 200, or the GE combo @ 225 RPM... now THAT is leisurely! It does seem "up there" considering it has no suspension! LOL I'd bet it would tend to "dance around" a bit especially if it was slightly off balance, unless they had something to control the "dancing".
Kevin