I cleaned the Mod 1888 Waltham in the same cleaner I always use - Zenith Formula 67. Never had a problem before but I have a new small ultrasonic cleaner. This is what the top plate looked like when I took it out of the bath. You can see where the barrel bridge covered the plate during use, but it wasn't on there when I cleaned it. The main plate shows the same "frosted" appearance but the barrel bridge does not. Nor do any of the other parts. It actually feels frosted or bead blasted yet the surface should be smooth and shiny. That's what it looked like before cleaning. You can see that even before cleaning the plate looks like someone etched it or something at some point. I don't think the factory would do that and if they did it'd be uniform over everything. Strange. I have no idea what could have caused it during the time when it was an orphan kicking around in someone's box of junk movements.