With the front cover removed, you can see the internal mechanism of the Master Lock #175 dials. In the image above, the highlighted areas are the disks - the "key combinators".
These are effectively equivalent to the cut lines on a key, when they are all lined up correctly, the dials can be pushed (under spring tension, as discussed earlier) so that the guard that is keeping the lock secured releases and the shackle now rotates in free space.
There are two ways to decode the lock using these disks. The most obvious is of course to pry the brass guard that is preventing you from seeing them, but in similar locks with a higher build quality this is not a viable option. It's also kind of cheating, so lets consider the trickier way.
The second way, which does not damage the lock, is much more akin to picking pin tumbler locks where you would individually manipulate the pins until they catch on the sheer line. In the case of the combination lock, your goal is to determine whether the gaps in the disks are where you believe them to be - or rather, that they are uniform across all dials (then all you need to do is rotate all dials until the correct position is achieved).
A slim piece of metal, again perhaps a ground down piece of a windscreen wiper blade or something of similar thickness and strength, could be fashioned with a small hook at a 90 degree angle. The technique here is to rotate each dial while feeling for the gaps (negative space) or solid material (positive space) in the disks so as to determine which numbers correspond to the negative space.
Alignment of all the disks in the same angle/orientation would indicate that you have the correct combination. Although, you will still need to rotate all the dials at once, one at a time, in order to figure out the actual combination due to the positioning of the key guard inside the locks housing itself.
There is a video on Youtube which describes this process, here.
Update (02 Sept 2013)
Storm Lock Picks have a great video on youtube that shows a Master Lock 175 being bypassed using one of their picks, here.
Kelly Alwood on YouTube has another great video that shows how these locks operate, including a good view of the locking mechanism, here.