John's Doggies... Delaware County, PA??

Grew up in Delco. & John's has the best hotdogs.  Originally in Chester... don't know if they're still there... a VERY DANGEROUS place to be, sadly.  Has another shop in Chichester.  Has the most amazing "secret sauce" that I'd LOVE to be able to duplicate.  Has come kinda very fine meat in it... assuming beef?  LOTS of garlic and VERY finely chopped onions.  Kind of a "brown" sauce... if there's tomato in there, it's very minimal.  It's NOT a chili.  As long as everybody gets the sauce, you're good... cuz you're gonna smell like onions and garlic for quite a while... not that there's anything wrong with that.
 
If you're familiar with that area, and have a CLUE as to what's in that sauce!?!