The service medal was first mentioned in 1895, but the first recipients were not chosen until 1898. It wasn't until 1899 that the award was actually made. This is, as the name implies, the service medal of the VOSJ. Throughout its history it has been awarded for conspicuous service of different kinds to the Order and not merely for length of service. Its usual use, however, is to reward extended service in St. John Ambulance or in the Order of St John.
The following description of the medal itself comes from the VOSJ's information sheet on the matter. The image below comes from our own personal collection.
With one small exception, the design of the Service Medal has remained constant throughout its history. The obverse features the head of Queen Victoria, modelled from a bust carved by H.R.H. The Princess Louise, Duchess of Argyll, together with the legend VICTORIA + D + G + BRITT + REG + F + D + IND + IMP. Originally this legend and that on the reverse were in ornamental gothic script but, since 1960, the current die uses upright seriffed capitals as printed. The reverse of the medal, between sprigs of St. John’s wort, contains five circles showing the Imperial Crown, the Royal Arms, the arms of the Prince of Wales as first Grand Prior under the Charter of 1888, the crest of the Prince of Wales and the pre 1926 Arms of the Order. Around the edge appears the legend MAGNUS · PRIORATUS · ORDINIS · HOSPITALIS · SANCTI · JOHANNIS · JERUSALEM · IN · ANGLIA. From its inception until 1942, when issue ceased for the duration of the war, the medal was manufactured in silver. Upon resumption in 1947 until 1960 alternatives involving base metal and silvering were employed. Between 1960 and 1966 the medals were silvered cupro-nickel and since 1966 they have been cupro-nickel, rhodium plated.
Interestingly, this is the only current-issue medal that still bears the bust of Queen Victoria.