The Mauser 66 is a fabulous rifle and you should buy it if possible. The one you’re looking at is a 66S Diplomat grade with upgrades. Options were were available separately, much like options on a new car. Pricing can be difficult, but that gun should bring at lease $2500. They were very expensive when new and haven’t really appreciated or kept pace with inflation, which offers the buyer a lot of value for the money.
66’s typically have great triggers, give rifle performance out of a carbine length gun (telescoping bolt) and are extremely accurate. Another key feature is the interchangeable barrels. Open the bolt, remove two Allen screws and the barrel comes right out. Additional barrels will all headspace, provided the chambered cartridge shares the same bolt face. Guns chambered for .243 will accept 6.5x57, 7x64, .270 Win, .308 and ..30-06 barrels (probably more). Magnum barrels won’t fit. Extra original barrels are very hard to find and can bring $600. It took me more than a decade to find a .270 barrel for my 66S Diplomat grade .243 and I was thrilled to get it. I know a gunsmith who makes custom barrels for these, but I wanted an original Mauser barrel. What’s the point of having a gun with quick change barrels, if you only have one?!?
Here’s a similar gun to the one you’re looking at that went for $4600 five years ago. Keep in mind that the auction gun came with two extra barrels, three sets of Mauser QD scope bases, QD rings, a Pecar scope and all barrels have iron sights. The extra goodies are probably worth around $2000.
https://www.rockislandauction.com/detail/65/3361/mauser-66rifle-243-win
Here’s a couple of photos of my gun. You’ll note mine have the same rail mount as the one you’re looking at. These rails bring about $150. Original Mauser QD pivot mounts bring close to $300 when you can find them and nicely made Russian copies of the QD mounts are available for about $250.
You can click on the photo to enlarge them.
I’m including some photos of the 1981 catalog and dealer price list. Note that the SL Diplomat in a standard caliber listed for $3500, with a dealer cost of $2625. The engraved telescoping bolt carrier for a standard caliber rifle was available separately at an MSRP of $749 (dealer cost $562). The engraved bolt knob and trigger guard were also extra!
The catalog is mostly eye candy, but it shows how far you could go with upgrades. Note that they also made a nice copy of the Colt Detective Special!
Four page centerfold of the Models 66 & 77!
The 66 Sniper rifle and the Colt clone!