I was requested by a friend to find out what this stamp is. Do you know what it says on the stamp?

I was requested by a friend to find out what this stamp is. Do you know what it says on the stamp?

After discussing it with my friends, the best result I can come up with now is

The characters beside the stamp characters are the corresponding ones that may be the candidates. Seal script samples are also given. Unfortunately, I cannot find a 100% convincing answer, because they can hardly form a meaningful phrase.
Character 1: 聞 or 查. Either is doubtful. If it's 查, it means the craftsman treat the vertical 丨 in 木 as two separate parts, then Character 5 will quite possibly be 木.
Character 2: 男. It's very doubtful because there're too many horizontals 一 in 田. I am almost sure it can't be 甲, because adding one important stroke into 甲 is very unreasonable.
Character 3: 天 or 引. Either is possible.
Character 4: 下 or 爪. Either is very possible. Specially, if if Character 3 is 天 and this is 下, 天下(the world, land under heaven) is meaningful.
Character 5: 木 or 大. Either is doubtful.
Character 6: 子. Well, it's the most confirmed one.
What I should clarify is that I don't mean the candidate characters are just what I am listing. There may be some more acceptable ones. This Chinese Etymology website may be a helpful tool for you.
I agree with Xu's arguments partly:
The scripts are seal characters or bronze characters.
There may be extra squiggles adding to the characters.
A Character may be separated into two (seldom larger than two) parts and written as individual two characters. In the stamp, there may be one case: 李=木+子.
But the case of the zigzag reading order 1-2-4-3-5-6 is really seldom. I personally believe it's in this order: 1-2-3-4-5-6, or less possible, 1-3-5-2-4-6.
Jens's answer, 鳳 凰 祥 雲, are not so similar to the character shapes in the stamp (notice that there's no 凰 in seal scripts; in ancient Chinese, it will use an "interchangeable" character 皇 instead).
EDIT
Character 5 may be also 北.

I don't have a complete answer but this is as far as I got, it was a lot of fun and hopefully this may help others. I feel that some real expertise will be needed to solve this puzzle!
查甲木引大子
There's some very fun tools which generate Chinese stamps in various scripts, which I used to make this image, which is as close as I got:

What's more important is that the characters make no sense! Perhaps they are encoding a person's name or date/time of birth using the Four pillars of destiny (生辰八字).
Some other information:
张 might be carved on a stamp as 弓长. No indication whether that was done on this stamp however.Some extra information would definitely help a lot, such as:
Here's my guess:
祥·鳯
雲·凰
The middle pair doesn't seem to be characters at all.