@Jay77,
thre is a way to termine whether its about 150 years or younger using Energy Dispersive X Ray . Take itto a Uni that has a geology department and ask one of the teachers or grad students (Undergrad students know ttrick but probably arent given free reign to all the equip).
So you take a very teeny sample location along the back, just a small area thats marked with two dots and the beam is shone between the dots (This is a quality control method where other experts may want to run their own bams over the crucufix). xpose it to an enrgy disp XRAY (EDAX) beam. If its old silver, then it wasnt refined with the high purity of silver smithing of the mid 1800;s and up. Most rally old silver has measurable proportions of gold, palladium, or copper(s high as 5%) whreas modern silver is of much higher purity
(PPB or less of other nobles)
If its got Cu to lvels of, lik 10% its even older (Id then rfer that to an archeology specialist thats worked in actual medieval metallurgy)
EDAX is usually a first step to take as there are really no good "wet,non-destructive mans" that wouldnt dissolve some of the metals
Irenee Supont, a famous industrialist , collector of artifacts had one of the biggest collctions of Paul Revere Silver and Medieval silver). It was written about and visited. AND admired by connoisseurs and experts of silver. The Univrsity of Delaware has a musm studis program that was st up by Dupont and it as that program that found out that 85% of Duponts collction WAS FAKE. And it was all done by non-destructive EDAX . So Dupont, rather than running an hiding, set up a program to actually assess fakes and fraudulent artifacts and, today its like the center of th Antiques world . The program is known as the Winterthur Program. Maybe you could contact them because they probably have even more techy means to determine ages of metal plate an jewelry. (They may do it free if they see that they can use the data as a "teaching moment" ), or you could enroll in their museum studies program because theres still fellowship and assistantship money for serious studies.
(not 100% serious about returning to school)