I have, but most of the belts we find around here were most likely from abalone divers (free divers). Sometimes the skill level and know-how with ab divers was a little questionable especially if they weren’t from around here and weren’t used to it, got bad info on setting themselves up etc. the belts I’ve found were probably lost on accident or dumped on the surface because the diver got overwhelmed and freaked out, maybe was way overweighted. I’ve seen guys with such massive weightbelts freediving that if they let go of their float tube they dropped straight to the bottom, not a safe or good thing at all. Most of the belts I find are huge! At least 35 lbs of weight or more. 7 mm is the thickest suit generally made and even in a brand new suit using that much tells me they were overweighted for ab diving. I have a whole bin full of salvaged weights.
No more ab diving though so probably no new weightbelts to find.
Too bad you can't make backplates out of lead....