I love this phono preamp but upgraded to a Manley Chinook.  The battery still lasts for more than four-five hours on a single charge.  I just discovered the two marks on the back side of the unit as I was taking pictures.  Looks like a manufacturing blemish because they occur on the exact same point in the aluminum chassis.  Below is the manufacturer's description.  You can also read a full review here: http://www.theabsolutesound.com/articles/musical-surroundings-nova-ii-phono-preamplifier/

Musical Surroundings Nova II Phono Preamp 

Built in California, the Musical Surroundings Nova II is a battery-powered phono stage with incredible flexibility and performance. The Nova II replaces the popular Nova Phonomena, and features dual-mono, discrete circuitry with extensive gain and loading flexibility, delivering the best sound in its price range. Like the Phonomena II and SuperNova II, the Nova IIhas rear panel accessible switches for easily accessible and highly flexible gain and loading adjustment. It features 2 rechargeable internal NiMH dual-mono battery packs with Smart Sensing auto recharge feature. All AC and charging circuits automatically disconnect when listening in battery mode. The Nova II features enhanced casework design and upgraded internal components.

"The Nova II retains all its forebears' virtues with considerably improved dynamic range, robustness, and perceived life and vitality. [Michael] Yee's designs are always very quiet and extremely transparent, and this latest one is exceptionally so, ranking up there with some of the most expensive phonostages I’ve ever heard. I cannot recommend it enthusiastically enough!"
– Paul Seydor, The Absolute Sound

The Nova II is a complete phonograph preamplifier with RIAA equalization that amplifies the output signal of a phono cartridge, either moving coil or moving magnet, up to a nominal "line level". The Nova II may be used with a receiver or an integrated amplifier. If you use separate components, a line level control unit (preamp) is required before the power amp, since there is no independent volume control for the Nova II. The Nova II's power supply is internal and connects to the wall with the supplied wall mount transformer.

• New casework with silver or black anodized finish


• Improved resonance isolation for main board and battery power supply


• 5dB better signal-to-noise ratio


• Super matched transistor pair input for improved linearity and sonic performance