My DGM engagement ring is probaby 95-100 years old (there's a date of their engagement enrgraved inside but the ring itself might be older. Its a diamond set with a raised cathedral style setting of small diamonds.
I never actually saw my GM wear it though. I gave it a clean with a soft muslin cloth and soapy water but would it be ok to go in an ultrasonic cleaner? Is the setting of old jewellery strong enough? The soapy water wasn't enough. DMother asked me if I wanted it but TBH its not to my taste but it is a family heirloom so deserves to be cared for.
I wear my Great Grandma's engagement ring (late 19th century). I wouldn't clean it without having the security of the claws checked. I have mine professionally cleaned about every 10 years, and each time it's needed at least one claw repaired. I go to Ernest Jones. They will assess the security of the setting for free, and give you an no obligation estimate. Have always been very happy with their repairs.