That looks very like the figure that I bought from Fusilier/Hussar, Chuck. When I say that mine is 54mm - I'm refering to the size of the seated figure - and not the height of the horse and figure from stand to the top. Yours could be an earlier version - with just a different style of painting to mine - as I prefer glossy.
As to use of Great helms - and decorations on them, many believe that they were used only at Tournaments - or Parades and not in actual battles. I don't really care that much - as my figures are Toy Soldiers - which I think look great if some decorative features can be added. I'm not alone here either - as Courtney, Ping and Greenhill models testify, many of which have detachable helms - and these can sell for really big bucks! ( so I'm not interested in buying any
).
It is known that by around 1350, Great Helms were largely being superceded on the battlefield by the more mobile Basinets and their like - as the Great Helms were heavier, less mobile and more cumbersome. In Tournaments however, they were still just as popular due to their great strength - even,(or so I've read), to being re-inforced with more metal on one side - to better protect the wearer in the joust. Straight ahead vision was fine here - though the death of the French King Henry II in 1559, in a joust - where he was hit in the eye form a broken lance tip shows just how dangerous a "sport" it really was.
There are quite a few web-sites devoted to both helmets and the rest of the armour worn during the middle-ages, and modern replicas of them, which are mainly provided for re-enactment groups to purchase. They are well worth a look - as they are instructive in how helmets and armour generally developed over time. A very interesting subject indeed. jb