This is the venerable classic hybrid tube preamp made by Sonic Frontiers, the SFL-1.
It's in very good shape, and hasn't been used in about a decade. I pulled it out of the box to list it.
I purchased it new in about 1997 and used it as my primary preamp until about 2001, when it was then put in my second system upstairs. After about 2009, it did get used at all, and I packed it away in the shipping box until now.
It sounds great and is working (just tested it).
I don't have the manual, but there isn't really one needed for this amp. Only thing to know is that the "direct" setting skips some of the switching and the balance dial, so it will produce the most direct signal path.