I found this so far.
You might want to read this as well.
Seems to be a lot of info on these guns but no details worth speaking of.
The best one I found was the first link.
Also this. It is a forum for Spanish made pistols. Star brand is in there so some one might be able to answer your question.
Also in looking for your answer I noted that your pistol is also called a Star M45. So when asking you can use that name as well as the Star Firestar 45.