The Shure SE1 is a tube phono preamp (not a mic preamp) that can be used for a variety of purposes. You won't really see this in recording studios, but rather you'll see it in an audiophile's home audio set up (if those still exist) or maybe even in a mastering room, which is the place that I've seen it being used. The SE1 is simple, with RCA connections to hook it up to whatever your desired application is. In this case, the mastering engineer I was working with had it in use with a record player. The tubes found inside the SE1 are four 12AX7's and one 12AY7. It has a built in power cord.
There's not a lot to using the Shure SE1 as there is just a high and low pass filter (at fixed frequencies of which I do not know), and a switch to chose between RIAA/flat, which I believe just changes the volume a bit. The SE1 is the type of preamp where you just will set it and forget it and let it do it's thing for whatever you're using it for - it's not a microphone preamp!!
The Shure SE1 definitely seems to do a good job as a phono preamp for a vinyl record player. Beyond this I can't speak to it's sound, but it's definitely an adequate preamp and it's tube so it has a very warm sound, although it's always hard to tell what's the phono preamp and what's the player, but I think the sound I was hearing had a good bit to do with the SE1.
There are very few Shure SE1's around, as I've only seen a handful of them being sold on the internet and it was totally random that I've seen one in action. I would think that most of these that are still around are probably broken in some capacity as these seem quite old. It's probably some of Shure's earliest equipment, but I can't say this for sure. If you do find one used it will probably be cheap, but good luck finding one!