Card with a description of the mirrors of Herschel's 40ft telescope. handwritten details concerning the speculum mirrors , on piece of paper which is glued on to card and stored in a brown envelope.

In ink, on the outside of the envelope is written:

'This mirror was found behind the great mirror in the Hall (when the Hall was being repapered in 1933) handwriting is JH's - but the statements therein need verification.'

The 'Hall' referred to here is at Observatory House in Slough.