On the back strap of this pistol it is marked Policia De La Provincia De Buenos Aires. This stamping indicates that this pistol was issued to the police department in the Provence of Buenos Aires which is the capital city of Argentina.
The stampings that are on the frame in the picture on the right are proof marks and year of manufacture marks. The first symbol to the left of the letter B is a tad hard to make out in the photograph but it is a knights helmet and shield with the X inside. This is the admission proof mark that appears on Spanish handguns submitted to the official government proof house in Eibar Spain after July 9, 1931. All proofing of handguns in Spain still occurs in the city of Eibar at the Banco oficial de Pruebas(official proofhouse) and the same symbol is still applied to this very day.
The "B" stamp with the * on top of it indicates that the pistol was manufactured in 1928.
The flaming bomb symbol that is seen just to the right of the letter B was introduced on December 14, 1929 and has the letter P inside the bomb for semi-automatic pistols or the letter R for revolvers. The flaming bomb proof indicated that a semi-automatic pistol was fired and had passed two proof loads, each of which was 30 percent more then the normal maximum operating pressure. This is then followed by two more rounds fired at normal pressure levels to determine whether the self loading mechanism is still functioning properly, if it was, then the stamp was applied to the firearm. For a revolver, where reloading takes place by means of the turning of a cylinder, an over pressure load is used. The letter for the date code with the asterisk on top is still in use as well, and today the letter is followed by a single digit number.
An interesting note is that Spain took longer to establish national proofing laws and standards for firearms then some of the other important firearms producing nations, notably Austria, Belgium, France, Germany and Great Britain. Although Spain began proof marking shotguns in 1910, it was not until July 18, 1923, nearly 5 years after the end of the first world war that Spain's proofing system for its pistols came into use.
Resource: Spanish Handguns by Gene Gangarosa