Spring driven with lever escapement with pin pallet escapement, 17 jewels. Alarm. Antimagnetic. Manual winding.
The alarm of the watch is set by turning the ring at the edge of the dial. At the 9 o'clock side of the case there is a thorn that stops ringing.
The company Sheffield Merchandise Inc. registered 13 June 1946 in New York, USA for manufacture of small watches and watch movements. Sheffield Watch Co., in turn, was registered in Biel, Switzerland.  It is likely that the watch was produced in Switzerland (Swiss made label is located on the dial and on the movement), and that the US company did the sales. According to some sources the mark on the movement – VOS means cooperation between the company Sheffield and the manufacturer of the movement – Voumard from Biel. 
 Mikrolisk : The horological trade mark index. URL: http://www.mikrolisk.de/show.php?site=280#sucheMarker (29.12.2011.)
 Ranfft Watches / 175: Gents Sheffield Alarm Manual Wind, ca. 1945 n.o.s. URL: http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2usau&1164816003 (29.1.2013.)