Direct Connection Valve Covers

I have another question about direct connection factory valve covers for a small block. Actually 2 questions

I have a set here that on one of them, has a gold sticker with black letters saying "DIRECT CONNECTION STAGE IV". Is there any significance in that? I know the 1st 3 "stages" referred to 413 and 426 Wedge engines.

Other question: going by shape and contouring, they are definitely factory Mopar parts, not aftermarket.
But I need to know how I can clean up the built up sludge on the back sides. I'm afraid to dunk them in anything for fear of damaging the chrome on them. And just a constant scrubbing in a solvent tank isn't gonna get them completely clean, not is it gonna get the built up crap under/behind the baffles