Thanks Ivo, you jogged my memory I recalled reading something about the Crystal Staircase. I've just been and had another read ... Freres Pannier took it over shortly after 1874 and had a workshop there as well, apparently getting their glass from the Freres Appert and decorating it in house for sale in the shop, if I've read correctly (Art of French Glass - Bloch-Dermant page46) - apparently the pieces had a diamond point signature of "Pannier-Escalier de Cristal". Presumably they sold pieces from others as well.
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