Hi Sophie,
First Quadruple I have seen. Good find.
Is the clear glass either yellow-tinged or orange-ish? Either way I am reasonably sure that the tint in the clear glass indicates a period of the general "Harland" years. But not sure at all which period (PY Co. / Harland / Highlamd).
For folk without access to Colin Mahoney's book, Masterworks the paperweights by Paul Ysart it was noted that "A three-layered Harlequin and a four-layered Harlequin are known to be in a private collection.