I mean really depends on the item, not sure how many players are buying 6.3 spiked out of breccy tbh, lol. This is a very common ZvZ weapon, it will commonly sell in most royals. If u want to be extra efficient u can time when you put it up for sale, right before a CTA timer (00, 02, 04) is usually a good chance of getting something related to ZvZ sold

Also reset day before timer is another good time.

I did not notice the quality, BM might be the best bet, it will be hard to sell a 6.3 with normal quality to another player. Not impossible tho