If the bass is older than about 5 years or so it wouldn't have come from the factory with a thumb rest.
Since it's a full acoustic top you can't screw a thumb rest into it like you would with a solid body. I added one to mine that's just a piece of wood held on with tape. Works well, but I have to re-tape it once a year or so.
As for how they sound, mine's an older non-midi fretless 4 and it sounds great. I have light flats on it and with a combination of onboard EQ and right hand postition it can go from Jaco-ish to sounding like an upright. It's a great bass. One of my favorites, for jazz and acoustic music.
The only minor down-side is that it has very high output. If you don't have an input pad on your amp you'd have to run the bass at under 50% volume.
Last edited by lz4005 : 12-02-2013 at 05:44 PM.