I'm certainly not Dave, but I'll say my 2 cents worth.
0504 has always been elusive. It supposedly was moved to Maine many years ago, to become part of either a tourist railroad road or a museum. At this point in time, I have never heard of anyone ever seeing it today.
It’s kind of like 0526 which used to be in the Salt Lake area and then disappeared to Michigan. Indeed, it was under lock and key for many years and now looks good on the Huckleberry Railroad. Pictures were posted her a few months ago.
Look at C&S 1008. We all knew it was long gone…..and wow. Found in CA
When I bought the 0400 in 1973, nobody knew where it went. Many folks thought it just plane vanished from Ridgway. When we moved it to Silver Plume in the late 1980’s, people were amazed that it still existed. Someone told me that it has been locked in a barn on a ranch in Colorado and was recently discovered. The reality is that all that time, it was on display….in plain view….at my home in Clifton, CO.
Hopefully we’ll have a happy ending to the mystery of 0504
Jerry