Reference 7928, the second series of Tudor's Submariner model, was launched in 1959 until 1967. Some rare example featuring military issue numbers such as the present watch, were most likely made for the Argentinia “Commando de la Infanteria de Marina”.
The Reference 7928 used the celebrated "Auto-Prince" calibre 390, a FEF (Fabrique d'Ebauches de Fleurier) based 17 jewel movement. It was available with different types of crown guards. The dials always featured the Tudor rose symbol followed by "Oyster Prince" to the upper half, the lower half generally the depth rating 200m=660ft, Submariner, Rotor, Self-Winding on four lines.
A similar example of reference 7928 made for the Argentinian Navy is illustrated and described in Tudor Anthology by Alberto Isnardi's, pp. 68-69.