My husband bought this machinery at a government auction, we want to remove the watermark in order to resell it. I've tried the spot healing brush, content aware fill, and cloning, but it's a bit tricky and doesn't look good. Any suggestions to make this easier? (We can't get the original unmarked photo). 
You own a photo with a watermark.
You can use Photoshop's tools to try to remove the watermark but it might be easier to re-assemble the machine. Photoshop was not designed to remove watermarks.
...And a forum filled with digital artists that are protective of their own work are not likely going to publicly explain a technique that would commonly be used by art theives (even if you claim legitimacy).
If you own the photo and the equipment, use the photo as-is.
If you need to, explain that this is the photo used to sell the equipment when you purchased it.
Someone interested in the machine can see what it is, and if you own the photo, then the people who put the watermark on it should have no problem.
Voila!
Craig
Thanks for your responses. I understand why you wouldn't want to explain how to remove a watermark, I hadn't thought of the obvious. I was not trying to do anything illegal, we do have rights to this photo. My husband has asked the sellers to search for the non-watermarked copy and send it on. A lot easier to do it the right way first....
Emily,
Removing the watermark from this is not really very hard. For an image like this, and trust me, there are NO real secrets in Photoshop, so don't worry about someone else illegally removing a watermark somewhere else, what you are going to want to do is to draw selections, either using the Path Tool or more quickly, using the Lasso Tool with the Option key held down to draw straight lines. There is going to be a selection for every skewed rectangle where the watermark crosses. Those selections are going to keep you from cloning where you don't want (don't use the healing brush here at all) and keep your cloning contained to the specific area. Once you get going, the entire project should take maybe thirty minutes and will look like the mark was never there. This is a simple straightforward retouch and since it's a photo you clearly have permission to use, hack away at it and have some fun while you're at it.
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