Yes the one you have been working on has been the color map. Specular maps differ a little bit, but to that much. You basicly want your raised features to catch your light. The only problem with your model is that you really have no detail in your model, It's all smooth. So a specular map on what you have right now will look kinda wierd unless you normal map your model. And for that your going to have to model raised features on your model making it high res. Make a copy of your model, model your detail. Then simply move your high rez model under your low rez ( do not combine them together ) and normal map it, and wha-la. You have raised features without increasing poly count on your low rez model and then your specular map will look work like it supposed to.

I did a little photshop on your metal texture to give you an idea how how your specular map works. Please do your own specular map. This one is just an example.