It doesn't literally mean "property of the hero." Although it often works out that way. A "hero" prop, in motion picture parlance, is a high-detail, nice-finish version suitable for holding close to the camera.
These are costly, often fragile items, and get swapped out for cast replicas when in the hands of background characters, or when the actor is rolling around in the dirt and would rather have foam rubber whacking them in the face instead of machined aluminium.
(A similar constraint exists with cosplayers and re-creationists such as the 501st; they may own a beautifully detailed real-steel DL-44, but they "troop" with something a lot lighter. Having foam rubber instead of metal also makes you more friends at the admissions gate to a convention.)
In theater, there are no close-ups. There is also rarely a budget to speak of. So all props are background props. The range in theater is not between stunt props and hero props; it is between well-made props and cheap props. It still doesn't have to look good in close-up, but a good prop is safe and strong and will survive multiple productions. A cheap one squeaks through until closing night because the running crew is pouring fresh hot glue on it every night.
I am deeply respectful of the skill set that allows creation of every bizarre thing requested by a director with no time, no money, and practically nothing in the way of tools, either. But it isn't something that personally interests me. Although it fits badly into the schema of theater, what I like to build are things that look nice from close up.
So the Lewis Gun magazines are done. And they took longer than they needed (they are basically a background prop). And although I'm getting better at getting a decent surface and finish, I'm falling down in getting a finished prop that is sturdy.
The gong I'm working on now will hopefully improve on that.
For the purposes of the show, a picnic plate spray-painted brass would be good enough. No-one is going to be caring if the props are realistic. But I want to do this for myself. I want to see if I can fabricate something that is light and strong and looks good at stage distance, but also satisfies me for close-up appeal.
Another of those lovely trade-offs is shop access. A good set of tools and supplies and a nice work space means you can dash off the "good enough" style of prop much, much faster. And since the shop itself is a significant sunk cost, the actual props you build are cheaper.
On the flip side, when you are growing your shop and your own skills, each prop is a significant investment in new tools and new methods.
This was always going to be such. I was originally going to resin the finished master for strength. But for weight, looks, and additional strength, I'm going to go back to slush-casting. With, however, an as-yet untried technique to add to my collection; RTV and a mother mold instead of a box mold and Oomoo.
I had some recycled expanded foam lying around so I cut the master out of that. Cutting the rough (on my also-recovered-from-the-trash scroll saw) was quick, but smoothing the surface has taken me the better part of two days. Of course a lot of that time was spent waiting on primer to dry.
I am about to spray the hammered finish (because I want that hammered look for the final gong, and it makes sense for it to be in the finished casting, not painted on to the surface). Which is always scary, because I don't think I can strip it if it goes wrong. But not that scary, because I'm not really happy with the shape I have. The center circle is too large, the bevel isn't tall enough, and the whole thing is maybe a bit small.
And, okay, this is why we say we work iteratively. I should have stopped earlier, before doing the final smoothing. But I went back, added an MDF disk to the center and Bondo'd out from it to increase the relief and make the proportions a little closer. And now I'm back to sanding and priming, hoping to get to the point where I can start casting this weekend.