I'd lay odds those come from the Florida Market. I haven't tracked down the source but several of the places have half smokes that are just as good or better than that stand. Granted the stand itself has the best half smokes I have found in a cart or restaurant.
Granted Weenie Beenie & Ben's Chili Bowl has the history going for it but I don't like that style as much.
The cart on 9th and Penn. is worth a stop too.
havent been to that stand, but one of the Canales places at Eastern Market has halfsmokes that are probably the same as Ben's. The casing is thick and snappy. The meat is chunky and they are pretty hot. There are two Canales places there, one sells halfsmokes that look like hot dogs, the other (better) one looks like sausage
if you want a cooked one, Union Meat in there too has em on hot dog rollers. Just on a hot dog bun though and not much fixins besides relish, mustard, and onions. But it is like $2 or 2.50.
Shocker, also at Eastern Market on weekends, the pretzel dog and limeade stand is awesome. Not a great value though. its like 3 bucks for a pretzel wrapped dog. Not a ton of meat, But it is very tasty. I think the pretzel keeps in all the hot dog juices