Gunther pond yachts are still made to this day in Germany. However, the Passat is a model which was discontinued some years ago.
We have not been able to find the exact date production ceased but this yacht is likely to be at least 30 years old. On the internet we did find this undated article from the US importer of Gunther yachts.
"We recently purchased the remaining stock of Passats from the manufacturer and are selling the last 4 available in the U.S., so don't miss out! 
The Passat is the largest in the Gunther line and one of the largest (not to mention fastest) freesailing boats on the market. It is a two-masted seagoing yacht with all the quality one comes to expect from this German Company. 
Of all the boats in the Gunther line, we’ve probably spent the most time sailing the Passat, mainly because it can handle anything. With its huge sail area and heavy lead-filled keel and it can haul out a hundred yards or more of line with ease. It's size also makes it easier to spot once it gets a ways out, unlike the smaller boats. Plus, it’s a real show stopper and attracts a lot of attention on the water. 
It probably also goes without saying that the Passat is a wonderful boat on display in the home, in a restaurant, etc. We've sold many Passats to first-time sailors and have recieved nothing but rave reviews. Don't think it's a mere toy, though. The Passat is definitely a handful. It's our most popular boat for adults to sail, based on its size and presence. It's a boat that will grow with you and teach you along the way. 
Specs: Ready to sail in less than 10 minutes Two masts with three sails for added performance Adjustable rudder Mahogany decking High-quality hull treated with special seawater-resistant lacquer Weighted keel for seaworthiness and non-capsizeability Ideal for almost any body of water, from ponds to the ocean. 
Comes with boat reel and line, sailing instructions, original box and display stand 
Wind range: up to 25 mph 
About Gunther GmbH. And Co. This German company has been in business for over 50 years and still builds the same high-quality boats people have come to expect from this company. They are a true representation of old-world craftsmanship and are considered by many to be the most durable and well designed model sailboats in the world. All our Gunther boats come with a 100% guarantee."
This particular yacht has not been sailed. We have found two small scratches on the starboard side and one on the port. Also the Passat name stickers are curling at the edges.
Apart from that this yacht is very close to mint condition.
This is the first time we have offered a yacht such as this but it appears that she sails very well and this example is in such great condition.