In the UK masters in mechanical engineering typically come in 2 forms. 1) MEng (masters of engineering) .. a 4 year integrated masters (essentially coupled to a bachelors and an undergraduate qualification) 2) MSc (masters of science).. a 12 month postgraduate masters, where you will need a suitable relevant undergraduate degree (sometimes also offering opportunities for more specialisation).
they are considered the same academic standard, MS as far as i am aware is notation often used in the US but just refers to masters of science.