John, I have an Oliver 50, but it is an ag tractor, not an industrial.  The last that I knew, Arnie Meyer in MN had a 50 industrial.  I don't believe that there were but a handful of the 28 industrials built. A few years ago, there was 1 for sale in TX, but I haven't ever seen one.  If I can help with any info on the 50 that I have, would be glad to.  Terry Allen.