I don't think it even needs to be high-quality or unusual, these days. A Mosin bolt-action rifle is not exactly rare, with 37 million made in total. It's also, with few exceptions (such as Finnish marksman variants) not exactly the finest gun in terms of build. 15 years ago, you could get one for $70. 5 years ago, they were going for $300 or so. These days, $600 would be a good find.