Your gun is a very fine mauser that was custom made by Josef Winkler in the Austrian Village of Ferlach. You might seek to get it restored but you might just leave it as it is. It is a very excellent example of the gunmaker's craft. I believe that any of the higher end gun dealers might be able to answer your questions with greater detail. Here is a start.
This is from the blue book of gun values by SP. Fjestad(sic)
Includes those firearms manufactured in Ferlach, Austria from 1558 to present. The Ferlach Guild (Genossenschaft) represented most of Ferlach's gunmakers until it was dissolved in 2004.
Many people mistakenly believe that Ferlach is a trademark - it is not. Rather, it is a small village in Austria where a gun guild was started as early as 1558. At that time, it was absolutely necessary that all the people involved in fabricating a firearm were located together in close proximity. This enabled the barrel maker, the stock maker, and the lock mechanism maker to work together closely to ensure that everyone was performing their task(s) correctly, effectively and efficiently. As the individual skills became better and more refined, more and more firearms were manufactured. Eventually, individual gunsmiths began to put their name on the barrel or frame of those guns which they had either manufactured solely or with the help of their fellow Ferlach craftsmen. Since all Ferlach firearms are essentially hand made per individual special order, very few are exactly alike. In the past, the gunsmiths of Ferlach have produced almost every type of shoulder arm imaginable, including such modern weapons as superposed and juxtaposed rifles and shotguns, hammerless drillings, repeating rifles, 3 barrel rifles, combination guns, 4 barrel rifles/shotguns/combination guns (called Vierlings), hammer guns of every type, etc. Some of these specimens represent the highest refinement in the gunmakers trade. Because of the almost unlimited variety of Ferlach variations, it is recommended that a COMPETENT appraisal is procured before buying or selling a specimen.
As is the case with many other European weapons, those models with desirable American features will generally outperform those with European specifications (i.e. a Ferlach sidelock combination gun that is 20 ga. x .243 Win. will be more valuable than a similar specimen chambered for 16 ga. x 5.6 by 50Rmm with sling swivels). Original condition and overall beauty are the primary factors to consider when contemplating buying or selling a Ferlach longarm. Other considerations include: type of action, difficulty of fabrication (Vierlings are very complicated to construct), caliber/gauge desirability, notoriety of gunsmith on barrel legend, elaborateness of embellishments, condition, rarity, accessories, and any provenance a specimen might have.
Today's master gunsmiths of Ferlach carry on the Old World tradition of quality in every respect. Most guns manufactured today are by individual special order with a wide range of calibers/gauges and other special features and options. As of this writing, these gunsmiths in alphabetical order are: Ludwig Borovnik, Johann Fanzoj, Wilfried Glanznig, Josef Hambrusch, Karl Hauptmann, Gottfried Juch, Josef Just, Jakob Koschat, Peter Michelitsch, Johann & Walter Outschar, Herbert Scheiring, Benedikt Winkler, and Josef Winkler. Anyone wishing to contact these master gunmakers should contact the indivudal gunmaker.