Iffy. Depends upon how you view XP in your world and the level distribution.
If your world is fairly high-level-heavy or epic in influence (like FR) then a "master blacksmith" will be 20th level and have 24 ranks in the skill, with Skill Focus and one of those +2/+2 feats. He will have traveled the world and teamed with dwarves and slain aurumvorax and rust monsters in their hundreds. He's not just a master smith, he's capable of standing with great heroes and using the weapons he designs. He's blessed by the gods with uncanny skill, and has invented new metals from scratch. Simple steel holds no challenge -- he forges faith itself into his masterful works of art. He's one of the greatest in the world, and all the heroes come to him for their gear.
If your world is less epic (like Eberron), then a "master blacksmith" might be 7th level, with 11 ranks in the skill, Skill Focus, maybe some synergy. There's no metal on earth he can't turn into a servicable tool with a little bit of elbow grease, but he's also not about to galavant accross the cosmos or forge spoons for the gods. He's a master blacksmith, but he's just a blacksmith.
If your world is more gritty, then a "master blacksmith" may be 1st level or perhaps 3rd or 5th at most. They'd have from 4 to 8 ranks, perhaps Skill Focus, but little else. They'd be defined by their ability to smith things, which not everyone in the world can do. Indeed, they'd probably one of the few people to put ANY ranks into smithing, They know how to work metal into items, and by the standards of the world, that's effin' magic, yo.
I'd assume a "typical D&D world" fits kind of close to the high end of that spectrum in the cities, and the low end out in the rural territories. So what a master blacksmith is really depends upon how much square milage is habitable, and how much is filled with small settlements vs. large urban areas.....
