Rusted brodie helmet

'ello chaps. Yesterday I bought a vintage brodie helmet, which seems that it was used by (i think) the british in the first word war. Here are some pics:

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

https://mail.google.com/mail/?ui=2&i...line&safe=1&zw

ok, you say, but what is the point of this post? Well, there are a few things I want to know , and therefore must ask you fine fellows here.

1. Who (or what) was MLS?
2.What does 61 mean?
3.If I wanted to clean off the rust, or clean it up in general, what should I do, and should I do it?
4. any other info you can give me.

Thanks.