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BRIAN PAUL EHNI
The picture I posted had 1959 Cadillacs. And the RI Color Guide by Steve Hile says the conversions started in 1958.
From: <main@RealSTMFC.groups.io> on behalf of "RICH CHAPIN via Groups.Io" <rwc27q@...>
Railmodel Journal Sept 1989 says RI converted 222 if those outside braced gons into piggy flats. Doesn't say when, but the pic with that article says "circa 1962"