Can't find any datasheets matching 17L50.... does sound like it could be a 5V though.
Regarding pinning, however, you'll find that some regulators - even in the same package - do have different pinning. The difference (in my experience) is between "standard" dropout regulators, which use an NPN pass transistor, and "low" dropout regulators, which use a PNP pass transistor. I presume it's to do with which terminal of the pass transistor needs to be bonded to the thermal tab - although that said, in a standard +ve regulator the tab is ground, which is not one of the pass element's terminals at all...
So the moral of the story is to check the pinouts for the exact device you're using - take it from someone who cam close to being caught out by this recently!