Rule Number One, which under no conditions must ever be violated, is very simple. Do not buy anything out of the Netherlands under any conditions. I could write for hours about this tip and the consequences of violating it but will just say "DON'T DO IT.
Inviolable Rule No. 2 is never buy anything out of the City of Los Angeles, California without negotiating a return and refund agreement with the seller using the Ebay messaging system. Both the Netherlands and Los Angleles have world class camera butchers working there who specialize in the ruination of Contax equipment, making it look pretty and then selling it on Ebay.
There's almost no way you can go wrong if you can buy a Contax with a lens on it for $50.00 or less. If you are going to pay more you need to keep some things in mind, particularly if you intend to use the camera to take pictures. The following tips are all based upon my experiences with Contax cameras purchased on Ebay. If you are interested in getting what you think you are paying for I strongly suggest you consider the following before moving forward to purchase a Contax camera on Ebay.
Please remember that most sellers are honest, but it is still possible to buy a bad camera from a sincere person who knows nothing about it and who believes it is in good condition. It is also human nature to accentuate the good points about a thing being put up for sale and to minimize its bad points.
My experience is a 75% disappointment ratio. This is to say that about 75% of the cameras I buy disappoint me when they arrive. Fortunately I have the skills, materials and resources to make most things right in a bad camera.
Before placing your bid be sure to ask the seller the following questions, as applicable, and receive a satisfactory answer:
One way of telling a very well used camera is to look at the top plate just to the left of the wind knob. A camera that has taken many pictures will have a crescent wipe mark visible on the top plate where the thumb has rubbed while winding the camera.
Another good tip is to import the pictures shown on the auction and then examine them critically by manipulating the size, brightness and contrast. Some sellers intentionally post very dark pictures to hide very bad paint and some sellers just don't know how to take good pictures. The black paint on a Contax will not show up properly unless the picture is lightened considerably. The way to import the picture is to place the cursor on the picture then click the right mouse button. Follow the menu to import the picture to a folder in your computer then use your picture editor to manipulate and examine it critically.
A good rule of thumb is that the camera will need a complete servicing in order to be reliable.
Another good rule of thumb is that if the camera looks really beautiful and is truly pristine it has a serious problem that prevents it from taking good pictures that no one has been able to figure out in the last 50 or so years. I have had the unhappy experience of purchasing some cameras that were very beautiful externally, but inside they showed the work of many desperate angry hands with tools in them.
There is another kind of beautiful camera to avoid. This is a camera that has been beautified through the use of Kiev camera external trim parts or a complete repainting using cheap black paint. There are some active EBay sellers working out of the Netherlands who are expert in exploiting the resolution limitations of the Ebay JPEG photographs to hide the small signs of a black paint repaint job, silver paint on worn out rusted screw heads, substitute parts, and other dishonest schemes designed to defraud honest buyers. There are even Contax I's being sold out of russia and the Netherlands with a very high quality modern plastic stick on artificial leather that is imprinted with very good looking Zeiss-Ikon stamps.
The simple fact of the matter is that Contax IIa and IIIa cameras are truly rare. In the days before Ebay it used to be a special event to see even one of them at a very large camera show. Ebay has made them seem to be relatively abundant but they are not. Because of this rarity there are not a lot of abundant sources from which one can choose. I have had personal experiences with all of the sources and have listed them below for your use.
When I opened them they were in completely original condition and they'd been sent to me because they didn't work properly. One was even sent to me from Japan. So understand that any camera you may buy from these sources will need a complete overhaul to be reliable and operate properly.
There's a huge list of Internet camera resources on the Internet. You'll find many Camera Stores on this list and you will find Contax IIa and IIIa cameras at some of them. The list is known as the Jeff Albro list. Here's the link to the Jeff Albro List: ALBRO CAMERA LIST
Here's a little tip about what USA Camera store "Excellent" really means. I know a Japanese seller who travels the camera show circuit around the nation. One day he confided to me that in Japan it is the saying that USA Excellent really means "Well Used". They're right.
Many people are hesitant to purchase a camera from Ebay because of the difficulty should there be a problem requiring a return and with the seller not being scrupulously honest and honorable. Everyone has heard an Ebay horror story. I've experienced several of them myself. I can always use my mistakes as part camera bodies and lenses.
There is a way around the Ebay difficulties as you will see in section 6 following.
It is possible for an extremely fine looking Contax to have spent a lot of time in a very humid atmosphere while it was in storage. A great many Contax IIa and IIIa cameras have been in storage for more than 20 years before being sold at an estate sale so that they can be sold on Ebay or the Internet. An excessively humid atmosphere is very good for the leather and has no effect on the chrome, but it is very bad for the internal components that are made of steel. I see a fair number of very fine looking cameras that have rust problems internally. Having me check your newly purchased camera will ensure you don't inadvertently buy a rust bucket.
This is a picture of the inside of a Contax II with Mint external cosmetics. The plastic electrician's tape is holding the shutter in place. There is a screw missing on the left and a metal brace missing on the right. If you look very carefully just behind the focusing knob you can see the little slot that holds the broken part of the brace that is still remaining. The screw and the metal brace should be holding the shutter in place. The owner of this camera purchased it from what he considered to be a very reputable Internet Camera store. The tape is very fresh. I have the parts to make this camera right and will use them at no additional cost as part of the camera overhaul. Do you suppose this owner would have purchased this camera if he knew it was held together with tape?
From the outside this is a true Excellent cosmetic condition Contax III. It is a real German made Contax body and all of its parts are German and original except for the shutter. It has a Kiev shutter in it. Kiev shutters range in quality from a "10" (equivalent to German quality), to a (1) (real trash). The shutter in this camera is a "-5" and is the worst I have ever seen. The winding shaft on the shutter is too short. In order to make the wind knob fit on the camera the shutter speed indicator bezel (the angled piece just below the winding knob) was ground down on its bottom. So much metal had to be removed from this bezel that its inner lip, by which it is held into place with two screws, was completely removed. The result is that this bezel is held into place by very cleverly made spring clips which provide just enough friction to keep it from flying loose when the film winding knob is lifted and rotated to change shutter speeds. The clips do not keep it from rotating if you pinch it in your fingers and twist.

There once was a time when there was only one kind of Contax I, II, III, IIa or IIIa and this was a factory fresh unit. But about 50 years have elapsed since Zeiss suddenly announced the end of rangefinder camera production. Since then every Contax IIa and IIIa has obtained a history of source, use and maintenance. Today, when a person sets out to find and buy a Contax IIa or IIIa, these factors need to be kept in mind in order to avoid cameras that have a bad history.
When Zeiss announced the end of Contax IIa and IIIa rangefinder camera production it came suddenly and without any notice. A catalog was issued to announce the start of the Contarex line and this catalog announced the end of rangefinder camera production and then end of all lenses and accessories for rangefinder cameras. At that time the Contax IIa cost the same as a brand new Chevrolet automobile. It was not just a "big ticket" item, it was a "huge ticket item" and there were people who had scrimped and saved for years to have one. The sudden demand was gigantic and dealers screamed to the distributors for cameras. In response to this demand spare parts were scavenged from every repair depot to produce cameras for sale.
A Contax I, II, III, IIa or IIIa camera is hand made out of hand made parts. This means that the parts from one camera will not necessarily fit into another. There are very wide differences in parts sizes from camera to camera. When cameras were made at the factory the assemblers had a very large assortment of parts from which to choose to assemble a camera. But when the spare parts or multiple parts cameras were used there were not so many parts from which to choose and some cameras were made that could not possibly work right.
Another element of complexity that enters this mix is that Zeiss introduced many internal changes to IIa and IIIa parts during the period of production between 1950 and 1964. There were three improvements to the mid range speed controller, five improvements were made to the rangefinder module, parts which were once bare brass became nickel plated, gold prisms were changed to platinum, the shutter tape was changed twice, all these are to name but a few. When a camera was made out of spare parts, parts from every time of production were incorporated into the camera resulting in a camera made out of parts that reflect the entire production history. So for a person like me who sees a great many Contaxes they are not at all difficult to identify.
The Contax IIa and IIIa are so valuable today that people are engaging in the same process now. Non working cameras are purchased at a low price so that parts from two or three of them can be combined to produce a high priced Contax for sale to unsuspecting victims.
My experience with these repair shop made Contax IIa and IIIa cameras is that they are always a lot of extra work and trouble to make right.
The question is, how can one avoid becoming a victim of a modern greedy camera butcher who is busy manufacturing Frankenstein Contaxes? The answer is that sometimes it's easy and sometimes its not, but it can be done and here are the main things to look for to avoid being stuck with a Frankenstein Contax IIa or IIIa: