Two optical Sun filters

Two sun filters, one dark green glass, the other smoked glass, in rectangular slide mounts for use on a telescope. Both glass filters are either cracked or blistered due to the effects of their use on the sun. Inscriptions indicated that they were used at the Royal Observatory, Greenwich and the observatory of Captain W.H. Smyth RN, at Bedford, England. It is likely that they were originally in the possession of Smyth due to his association with the United Services Institution.