My daughter needed something from her mother's house. I complied and found a rare box of my family heirlooms?

while getting my daughters passport for her, I found a small box of heirlooms my Grandfather and father gave to me. When we got divorced I forgot those items or thought I had them. Yes, I agree, I should not have taken them. My ex-wife has threatened to call the police if I do not return them at once. Why would she want my heirlooms that are value only to me. How do I get them back?