curio - noun, any unusual article, object of art, etc., valued as a curiosity.
relic - noun a surviving memorial of something past. an object having interest by reason of its age or its association with the past: a museum of historic relics.
Curio and Relic License - noun, A regulation implementing federal firearms laws, 27 CFR ยง 478.11, defines curio or relic (C&R) firearms as those which are of special interest to collectors by reason of some quality other than is associated with firearms intended for sporting use or as offensive or defensive weapons