Good information to have. I've only been seriously interested in C&R handguns for about a year now, and I'm trying to educate myself about what to watch out for when shopping for collectible pieces (no Krieghoff lugers
or suchlike, but just those old guns that are affordable for me yet interesting from an historical viewpoint).
On old Smith topbreaks, another dead giveaway is a nickeled (or blued) hammer and trigger. These parts were case-colored originally; no need to even pick one up for closer examination if they are not.
It's nice to have a sure-fire way of telling a refinish, at least on those particular guns. From what I understand, a related "tell" applies to the factory nickel finish of the little FN 1905 .25 pocket pistols - the trigger and safety were in the blue originally. I recently encountered a totally (re-) nickeled 1905 whose owner didn't volunteer the information that that the nickel was not the factory finish (maybe he didn't know). Fortunately for me, I was in that case sufficiently informed not to spend the $400.00 he was asking for a non-original specimen.
I heartily wish people would leave these old guns alone. Most of those that get refinished are destined to be left out in the cold by collectors and others who would value them - though I guess some find good homes with those who want a shooter or simply don't place importance on originality.