I got 2 corny kegs & a glass carboy at a garage sale 10 or so years ago for like $25. One of the 2 kegs I've never used and recently gave it a cleaning with a PBW soak overnight and some scrubbing. I got most of the residue that was in there out, but the bottom does not look that great. Do you guys think this is salvageable, or should I toss it? I was considering getting some bar keepers friend to see if it can clear up those marks. If this is no good, likely going to pick up a 6g torpedo keg.