Pentax-F AF adapter 1.7x

I received today an 1.7x AF adapter that I recently purchased. When checking the condition of the adapter, I noticed that there are some stains on the glass. I have tried wiping the glass with a microfiber cloth, but the stains do not go away. The stains are best visible when blowing a breath of air onto the glass (which I also have done with the photos below). Could this possibly be oil of some kind? Any suggestions to what this could be?

Regards
Bjørn

[IMG]http://i812.photobucket.com/albums/zz50/bjolester/AF_TC_2.jpg[/IMG]

[IMG]http://i812.photobucket.com/albums/zz50/bjolester/AF_TC_1.jpg[/IMG]

Thank you for your answer! I believe it is under the glass. Maybe this is then a "lost case", perhaps I should return the adapter to the seller?

Thanks! How could one remove the condensation if this is indeed the problem?

Thank you Mike! I will put it in a box with silica gel packs, I guess that is about all I can do. And then wait and hope for the best... I can/will also return the adaptor if it becomes 100% obvious that it has problems with coating or cement.

I know it is very difficult to give any diagnosis of the adapter glass based on my pictures, but I have already gotten very valuable advice. Anyway, here are two more photos of the glass. The second one is taken after having breathed air onto the glass.

[IMG]http://i812.photobucket.com/albums/zz50/bjolester/AF_TC_3.jpg[/IMG]

AFTER BREATH OF AIR
[IMG]http://i812.photobucket.com/albums/zz50/bjolester/AF_TC_4.jpg[/IMG]

I have tested the adapter with the A35-105 today, and the images I get are very good. It seems as if everything is just fine when using the adapter on the K20D... Maybe the stains on the glass do not have any negative impact on image quality when using the adapter with a 1.5 crop sensor? The adapter is unused and the price is very good, so I really want to keep it. Hm... what to do:

What's the price?

Thing you have to remember is that the marks will affect resale value should you ever wish to sell it..

If on the outside they may be the result of an attempt to clean the glass, and might come off if you use acetone or a proprietary lens cleaner.

G

About GBP 140,- with pouch + box + instruction (Made in Japan). And it is unused, 100% mint (except for the #$%!! stains on the glass:cry.

Owch that is a good price ... still not sure I would be happy though. Just looked at mine and its crystal clear, that one seems to be going all round the rear element. Is the front element ok?

Any chance of knocking the seller down to £100 because of the marks?

Edit: have you tried cleaning it as George suggested?

Keep it, or sell it to me for £150
Davex.

That could be a possible explanation. I will buy some lens cleaner on Monday.

The front element is 100%, it is only the back element that has stains. Yes, I could try to negotiate the price if I decide to keep it.

Change of heart?