Treat them with respect and common sense, use the good advice you see from members here, other places and good research online.
There are threads here and websites elsewhere giving detailed good info about lead rot, treatment and prevention, alloys used and varying qualities over the decades.
I have miniatures dating back to the 70's with variable lead content - rarely I would say as much as 40% but high amounts in the alloy is expected in some cases.
I have no rot on any that I am aware of, lucky me. None of them have come close to affecting my health.
none are from the 19th century though, the manufacturers in question are categorically 20th century in origin.