I've noticed one word largely missing from this thread, documentation - any time something is done to something in a museum collection, it should be documented in the object's permanent file.

For example, a piece of structurally-essential wood must be replaced. That's removing "original fabric" but must be done for safety reasons. The record of the change (wood species, dimensions, etc.) would be noted in the car's records.

Removing paint for any purpose is obviously removing "original fabric" and is also removing the record of the entire color history of the car! With modern technology, some good paint chips in the car's permanent file can be used to get a precise Munsell number for any layer in that chip, and other evidence can be used to date the layer. The process is not cheap but can answer the question.

As to "old beat-up trains," first collect and document the train's entire color history, then note in the files what year you are restoring it to, then strip and paint as desired.

Al, that’s a great point. Is it common practice at any railroad museums to document work in this way? I agree it certainly should be - but it’s several extra steps in an all ready time consuming project.

It's not always much additional work, for example file copies of all purchase orders, receipts, packing lists, etc., in the file for the object being restored. These papers all carry good dates and descriptions which is what documentation is all about.

Once documentiation becomes a habit, it's quite easy to save the necessary information in many cases.

If a museum has an Archives Department, it can be very helpful. Also the folks who write your checks can help out.