Much like pure gold, pure silver is a soft metal. Too soft to be made into jewellery because it would bend out of shape too easily. Especially children's jewellery, which might be overly fiddled with by little fingers. So, a harder metal is added. Once upon a time, it was nickel, but nickel has been shown to cause skin sensitivities so these days, the harder additive metal is usually copper. Wikipedia says:
"Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925."
Most will have seen sterling silver written as "925" or ".925" - meaning 92.5% is pure silver, rather than 100%
It is still possible to purchase pure silver jewellery but it is rare and we do not stock it because we want our customers to enjoy their baby jewellery and children's jewellery items for years, and even to hand them on to the next generation.