When most people give valuation advice, it is often based on what they would be comfortable paying for the item and not always consistent with what the market would bear. Price for K98 rifles is based on rarity, originality, the number of matching parts, condition and the venue it is offered in.
Your rifle is extremely rare and if pictures bear it out to be what you describe it to be, it will be the first matching 337 1939 I've ever seen. It does not mean others are not out there, it just means that I have been collecting for several years and have never seen one. Originality is key. As others have said, you need to add better pictures, particularly of stock markings and serial numbers. From what I see so far, nothing jumps out at me as being wrong. It appears to be in solid very good condition.
Venue is important too. From experience, the rifles I see commanding the highest prices are run in on-line, no reserve auctions on sites like Gunbroker or Auctionarms. If you go this route, make sure your title has "K98" and "98K" in it and run it for two weeks. In the end, there will be a small fee to the Website (1-2%) and you'll need to send it to a licensed dealer or collector.
Taking this rifle to a local gun show, pawn shop or gun store would be a waste of your time. These rifles are a niche market and while many people know they are valuable in general, few can tell original from fake or rare from common. To limit risk, most dealers and show attendees will make low offers. Even if a dealer knows what it is they cannot offer full retail and make a profit. While you may meet a collector at a show, it is not likely they will be willing/capable to pay a high retail price. In short, if you go this route and ask a high amount, expect a lot of blank stares, some laughter and counter offers in the $100 to $2,000 range.
Once it is validated, listing it on the forum trader here is another good option. If original, this rifle would easily be worth $3,500 to $4,500. A 39 BSW, the predecessor to this rifle, recently went for $4,100 (
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=248442715 ) and I have seen others. I believe the 337 is tougher and would command a higher price.
Finally, you will likely be getting a lot of PMs and e-mails from members looking to buy it directly. Some will offer a fair price and some will not. Keep in mind these people will be the same ones bidding if you offered it in auction so you will not lose much if you do not take their offer.
To recap, validate your rifle, take your time and if selling it is your goal, the auction is the route to go.
Hello folks, glad to have found this board.
Thanks in advance for your help.
An auction doesnt mean you will always get top dollar. It does happen and can happen. But there is no way to know for sure. I much prefer, and most do here coming up with a price on our own and selling it here before going the gun-broker route. It's a last resort. 
