coffee suggested:
Sounds like its just a build up of wax and grease. Ammonia will take it
right off for you. Look like brand new.

NickySantoro wrote:
Spic n Span and a good dose of ammonia. Do it 4 times.

OK, guys, ammonia it is. I'll have a couple of people hit it hard on
the next clean-up day, and bring the results back here. Thanks!