We have one here in Nebraska, at the SAC museum between Lincoln and Omaha. The thing is up on a pedestal in a diving pose as you walk in the main door 2-story lobby (which is all glass and glass roof). You cannot touch it, but by looking at it you can see that it did degrade a bit when it sat outside at the old museum.
From what I know about the A-12 and SR-71s is these tidbits.
1. Single seater is the A-12, designed as an interceptor for Russian super fast bombers. Yes, they lauch missiles from a bomb bay.
2. SR-71 name is a mistake made by the chief of the Air Force when giving a presentation to the President. He goofed when he was supposed to say RS-71. All recon planes ID's start with the letter R, but nobody is going to correct the head of the Air Force, or the President.
3. The motor oil of engines is almost solid at room temperature. They had a hell of a time figuring out how to get it to work. I believe they got it working somehow, but it isn't pretty. Electric heaters perhaps?
4. The engine intake cones retract into the nacelles when going full speed.
5. The plane does not handle bursting through the sound barrier that well (unstable). They do it in a dive to get it over with as fast as possible.
6. The engines are dual turbojets and ramjets. The high speed flight is with just the ramjet part.
7. Most of the thrust at high speed is actually suction from in front of the engines, not the exhaust comming out the back.
8. V-8 or V-10 engines used in race cars are used to shaft start the turbojets on the ground (stick the shaft into the engine and spin it up...it doesn't have onboard starter motors).
9. It does leak fuel on the ground, which is a different brand of fuel with a very high ignition temperature. JP-12 I think. Lockheed (Kelly Johnson in other words) never found a resonable sealant to use on the plane, so it never was sealed.
10. The tools used to work on the plane have to be the same Titanium used to build the plane. Early on the Chromium plating of regular tools was leaving residue behind that normally is not a problem. At very high temperatures it reacts with the titanium, and the plane often loses rivets when their heads were popping off.
11. SR-71s have flown over Russia many times, even though Gary Powers was shot down in the U-2. The Russians didn't make it public because it was embarassing to admit they cannot stop them.
Most of that comes from Ben Rich's book "Skunkworks." Ben Rich was the guy who took over the Lockheed Skunkworks after Kelly Johnson retired for health reasons. Ben Rich did the Stealth F-117, which oddly Kelly Johnson didn't think would work.