The data I was going to put on it weren't that valuable, mostly music and phone photos - I wasn't that distraught when I snapped the old SD card. A quick test that it wasn't completely fake would have satisfied me.
Agreed. Electronics hackery, especially making sense of someone else's circuit, takes a lot of acquired knowledge. Knowing common circuit topologies and being able to identify them when you see them, knowing that if you see a component in a TO220 package there's a 95% chance its either a transistor or a linear reg (usually you can guess more specifically just from its location on the board), having a mental list of components you can use to design a certain circuit (hmm, an audio preamp? I wonder if an NE5532 would be suitable?), knowing that a yellow bipedal surface mount thing is almost certainly a tantalum cap, knowing that a number of connectors near a SoC is probably JTAG etc. All of this just comes from experience and recognising patterns! Although I imagine dealing with code is somewhat similar? Perhaps there are certain things which you come to notice by instinct? Eg maybe you can look at some assembly and, just skimming over it know that it's supposed to be a time delay?
This seems about right. I found various components inside with date codes ranging from 1996 to early 1997. The indicator lights had no markings on them, but IIRC the bulbs inside were 28v incandescents. Do you know any more about them? I'd be interested to know what IP rating they have (IP67?)