Also found this about the medal
This medal was instituted in 1845, and is still on current issue. It is a most unusual and complicated award, with differing types and reasons for award. It is necessary first to explain the setting up of the award. By a Royal Warrant of 19th December 1845, a sum of £2000 was provided each year to be given to NCOs of the rank of Sergeant and above in the form of annuities, to be paid for life. Recipients of these annuities were either serving or retired NCOs. In addition, the annuitants were to receive the Meritorious Service Medal, which was instituted at the same time as the annuity fund. The annuity and medal were to be rewards for 'distinguished or meritorious services'. Because the annuities were paid for life, and the sum of money available was limited, it follows that the number of MSMs has always been very limited, especially in the earlier part of its issue. Awards were evenly distributed amongst all regiments and corps, and so early MSMs to any particular regiment are very rare on the market. The sum of money available for annuities has been increased on several occasions since the institution of the award, but the yearly figure for issued MSMs has remained low. As the overriding aspect of this award was financial, awards were listed in Army Estimates from 1847 to 1926, and from 1885 to 1972 lists of recipients were published in Army Orders. The MSM has always been issued as a form of reward for long service to senior NCOs, although there are two exceptions to this statement, one minor and one major. The minor exception is a few early awards which were stated to be for gallantry, whilst the major exception is during the period 1916-28. During this period, MSMs were awarded for services in the field which fell short of the award of the MM or DCM. A very small number were awarded for gallantry not in the face of the enemy. This usage of the MSM ended in 1928 with the introduction of the BEM for Meritorious Service. Thus between 1916 and 1928, two types of MSM were awarded; firstly, the limited regular issue to annuitants for long service, and secondly, the large number of awards for services during the war. These two types can be told apart by the fact that the 'long service' issues have no mention of the recipient's number on the rim, whilst immediate awards for services in the war have the recipient's number. The vast majority of MSMs have been awarded to British Army personnel, but there are some rare Colonial issues known such as Canada, Cape of Good Hope, Natal, and the various Australian states. These are similar to the British MSM, except for the name of the Colony or Dominion on the reverse above the normal inscription.