I believe (and don't shoot me if I'm wrong) that this panel is designed to be outside in the elements AS IS.
Here is some promotional text copied right from the Alternative energy store website
http://shop.altenergystore.com/itemdesc~product~Ip50f,+50w,+12v,+Fiberglass+Solar+Module~ic~INN50-IP
50F~eq~~Tp~.htm
"These are high quality lightweight fiberglass (FRP). The seven modules listed below are targeted at 12VDC power sources and are used in applications such as logistics tracking, asset management systems, off-grid lighting, mobile communications, mobile computing, recreational vehicles, gate openers, water pumps, signaling devices and surveillance cameras."
I don't think that a commercial solar panel manufacturer would have much success with a solar panel than couldn't withstand the rain since the only good place to really mount them is outside.
The coating is probably rough to the touch because it reduces the amount of sun the panel reflects from the surface coating. This will make it a little more efficient because more light is reaching the PV material.
I have one of the 5 watt Sol charger panels that is covered in a fiberglass resin and I actually use it submerged in water for concentrated solar power (CSP) applications! I focus concentrated solar power into a hot water collector with a 5 watt solar panel inside. The water keeps the solar panel from melting and heats the water at the same time. Then we use the electricity generated to power the recirculation pump. The panel under normal sun will not power the recirculation pump at all but under 9x CSP the 5 watt panel is producing about 20 watts. Here is a link to a 7 hour time-lapse of the heliostat at work and a data chart of the energy that we were able to capture with the collector.
http://www.heliotrack.com/tl9x/index.html
So, IMO, put it outside as is.
Remember that many boats are made from fiberglass.
Justin
www.heliotrack.com