Oh yes, there are quite a few ways to handle that sort of thing. At its simplest, click on the history tab to see a list of all the edits made to an article in reverse chronological order. Then click on the date&time; of the last good edit to see the page as it used to be (in this case, that would be click on the 22:15, 9 September 2005 edit by User:Tsemii but avoid clicking on the username itself). Now click 'edit this page' and in addition to the normal edit box you should also see a warning at the top that you are editing an out of date version of the page. That's OK, in this case it is what you want. Don't make any changes to the text, just enter an edit summary like 'reverting to last good version by xxxx' or 'rv test', press the 'save page' and you are done.
Another way, is to bring up the page history, then click on the word 'last' to the left of the bad edit. This should bring up a page like this highlighting differences made by the bad edit. You can get a similar page by clicking the 'diff' link from your watchlist. Then clicking on 'Revision as of 22:15, 9 September 2005' at the top of the left panel, will take you to the earlier good version, and you can make a null edit and save as before. The advantage of using this page difference approach is that there are also links to go forward and back to newer and older edits. So if a vandal has made a series of bad edits you can keep stepping back until you reach a good version of the article before editing and saving to revert to that version.
If a user is looking like being a problem, you can drop them a note on their talk page, asking them to stop. There are a number of templates for boilerplate warning messages which escalate from  to . Typically if a user has recently had one of the earlier test warning, you add the next one in the sequence and sign it. However, if you are reaching test4, its a good idea to get an admin involved because the next step is to block them.
If you have the time, you can also check the user's other contributions to see whether they have been messing up any other pages, and if they have, revert those pages too. However, if they look like being a particularly busy vandal, its usually best to get help from an admin at Wikipedia:Vandalism in progress, because admins have some extra 'rollback' buttons to make it much easier to undo a large number of changes.
I've reverted the particular edit at Agricultural machinery, but this one just looks like a harmless test, so no further action was needed. Many anon users still find it hard to believe that their changes really are for real and immediately visible to everyone. So we see a lot of random edits like this.
There is a better guide is to be found at Wikipedia:Revert.