its a dutch army one - modelled on the later US one with smaller handles, fits the US style bottles copied by a few armies. little smaller than the US and Crusader cups but average price under a fiver they are a good buy. I've got one in the cupboard somewhere and used it for years after I lost my first US one.
the only drawback is if you boil a brew in it its hotter on the lips than the other two as the edge is rolled over so the heat doesn't dissipate. a bit of insulation tape solves this.
they never had metal bottles with them. all the issue US style bottles will fit as will the civvy copies but they are often a little bit smaller. best thing is to find an american one with cover then you wont need to buy a pouch for it. buy the proper bottles though - should cost 4 quid on their own but do a search.
the germans also issued the same mug and might still do.
web tex use a similar cup and a copy crusader cooker in their 'warrior' cookset but neither are up to the job. it will work with a crusader cooker if you want it to. if you want to make a lid then use thick foil.
let me know if you want a source and I'll stick some links up