Precision Optical Protractor Carl Zeiss (0884)
Info
Optical Bevel Protractor for precise measuring of angles. The legs are set to the bevel after which the angle can be read by looking into the very small viewing hole. The scale reads from 0 to 90 to 0. Each degree has 6 subdivisions (5 lines) which would give the instrument a precision of 10 arcminutes.
The locking button reads "Los" (Loose) and "Fest" (Fixed).
The box is painted wood and also bears the logo of Carl Zeiss on the top lid.
Inscriptions:
CARL ZEISS
JENA
On the side of the fixed leg:
329 (Could be the type or the serial ?).
References/Links/More Info
Practical Machinist - Thread Optical protractor
Google Books - Handbook of Dimensional Measurement - Page 255