The registry collects old, durable, documented physical objects that might one day support comparison studies. It is not a list of remarkable artefacts and it is emphatically not a search for special ones. What we are asking is narrower and duller: which objects combine physical longevity, a measurable response, a reconstructable repair history, identifiable custody, and lawful access well enough to support study over a long period?
Most do not. An object may be four centuries old and useless to us because nothing about its past can be checked. Another may be from 1890 and excellent because every intervention it has undergone is on an invoice somebody kept.