English, c.1840, engraved across the crossbar 'Marrat, London' the compass with printed green floating card with locking lever, fold-up sight with reading prism and fold-out viewing slit in a clam-shaped case covered in Moroccan leather and lined in cotton-velvet, compass diameter 10cm

Footnote: according to Clifton John Symonds Marrat is recorded as working in London between 1832 and 1875