Davis Mark 15 Master Sextant 
Mark 15 Sextant
This model has many great features including seven large sunshades, a 3 mm x 27 mm star scope, and easy-to-read micrometer drum vernier scale that reads to 2/10 of a minute. The Mark 15 has a 7" (18 cm) frame radius graduated from 120° to -5° and comes with a traditional half-silvered mirror.
Comes with instruction booklet.
Owner's Manual (pdf)