I've always been fascinated with this locomotive and how it managed to be the only narrow-gauge locomotive which operated in my relative area to escape the scrapper. It's unfortunate none of the South Pacific Coast engines made it to present-day (unless those tall-tales-on-rails out in the Mountains become truth!), but at least the "Jupiter" made it, not to mention some remaining rolling stock which served the SPC up at Ardenwood and elsewhere.
First saw the locomotive in a picture hanging in a South Bay restaurant's restroom (!) as a kid; the famous shot taken while the engine served the SCR. Visited it several times over the years while in the DC area visiting family. Haven't seen it since the move from the Arts & Industries Building.
I'd love nothing more than to see the locomotive return 'home' and away from the Feds; while I doubt it would happen. I always wondered if the Smithsonian would trade such as the NPS reportedly did with the Steamtown collection...
I heard the locomotive was retired from the IRCA around 1960 as well; didn't actually make its debut in the Smithsonian until 1976. It sat out in a park in DC for some time; I don't know about the rest, or how long it sat there. The restoration is, in a word, 'interesting; seeing it look more like Charlie Ward's sketch (the Roaring Camp herald), even if it remained a display, would be nice.
Seldom mentioned is the 1875 Baldwin out in Minnesota (a Mogul) which, although it never operated on American soil, is a pretty darn neat engine. It's displayed indoors at the End-O-Line Railroad Park, after almost becoming an amusement park engine in Illinois. Like the Jupiter, it's cosmetic restoration gives a lot to be desired (while the Jupiter still beats it, obviously, by far.) Was up in Rhinebeck, NY at some point; I believe the same collection as a 2' 'Americanized' Henschel or something that was out in Colorado as well at some point.