The description for the tea set *says* that this piece is a strainer, but it also says that it's made of brass. I'm about 99% certain that it isn't brass (unless they plated and artifically aged it) and about 50% certain that it's either pewter or silver based off the oxidation patterns and texture. I'm leaning more toward pewter than silver just because I don't see any evidence of the rainbow-ish opalescent effect that tarnish often has on silver teaware. I mean, it could even be old steel, but I don't think so somehow. Steel tends to rust as it ages, even stainless.
I was hoping that you guys may be of some help, because I've already spent 60+ hours scouring the 'Net. One thing that makes me think that this may have been something like a porringer repurposed into a strainer is the hole pattern. All of the non-woven tea strainers I've looked at have patterned, deliberate hole patterns, but this one just looks almost like someone used a tool like an awl to pop holes into it.
I'm just hoping that someone may know something about this.
...Even if it's just to say, "This isn't real teaware, you fool!"
