This is where you need to go to ask the question:
It looks orig. and looks like it's a #2 "Simplo Safety" pen but is hard to see, you may have to take more photo's before posting in the forum above to get a good answer. They hardcore over there.
I grabbed some info off the WWW for you.
I think the pen is from the 1920's, made in german factory in Hamburg. They made a octagonal version as well, they're much much rare. The nib retracts back into the pen when you twist the top of the pen. You definitely need to service it and that can be very expensive. Maybe not really the best fountain pens to write with in these modern times compared to other nice fountain pens out there.
The name Simplo, derived from the word “simple”, describes the decisive advantage of the Simplo Safety Filler. They could be carried safely in any position, as they were virtually leak-proof when closed. With its filling mechanism it set itself apart from the desk-dip pens most common at the time.
The four holes which serve to equalize pressure and prevent leakage of ink when opening the cap, body is made in black ebonite.
In 1907, Sheaffer began marketing this type of fountain pen which quickly became a reference for the rest of the companies because of its retractable nib which allows to close the tank when the fountain pen was closed (as a top) thus preventing ink leakage.
Turning the rear section retracts the nib
The screw situated next to the nib commonly posed an important problem. To “thread” at the top of the head piece, the cap may facilitate breakage,to solve this, in the interior of the cap carries a small bar disposed which penetrates inside the feeder (practiced in the central channel to the effect) thus anchoring the body with the cap, since it is concentric and united with it, releasing a part of “burden” to the thread and bringing greater stability and longevity to the pen. The “central channel” on the feeder provides extra support to the entire cap / body.
Probably worth around $400 as is but they go as high as $1,500. Your pen looks like it needs a full service luckily there are still some very good repairman who can service this pen but it's not cheap, especially if the nib needs restoration. The higher the number on the pen the more valuable it is, you have a #2.
Edited by Devoti - 6/10/13 at 1:04pm